U.S. patent application number 15/250056 was filed with the patent office on 2016-12-15 for modified leucine dehydrogenase.
This patent application is currently assigned to AJINOMOTO CO., INC.. The applicant listed for this patent is AJINOMOTO CO., INC.. Invention is credited to Wataru Hoshino, Yuya Kodama, Toshimi Mizukoshi, Uno Tagami.
Application Number | 20160362662 15/250056 |
Document ID | / |
Family ID | 49260189 |
Filed Date | 2016-12-15 |
United States Patent
Application |
20160362662 |
Kind Code |
A1 |
Hoshino; Wataru ; et
al. |
December 15, 2016 |
Modified Leucine Dehydrogenase
Abstract
The present invention provides a means and method useful for
measurement of a total branched-chain amino acid concentration.
Specifically, the present invention provides a modified enzyme in
which at least one amino acid residue is mutated so as to improve a
property of a leucine dehydrogenase which is associated with the
measurement of the total branched-chain amino acids, such as, for
example, substrate specificities of leucine dehydrogenase for total
branched-chain amino acids, activity of leucine dehydrogenase for
any branched-chain amino acids, and thermal stability of leucine
dehydrogenase; and a method of analyzing the total branched-chain
amino acids, comprising measuring the total branched-chain amino
acids contained in a test sample using the modified enzyme.
Inventors: |
Hoshino; Wataru; (Kanagawa,
JP) ; Kodama; Yuya; (Kanagawa, JP) ;
Mizukoshi; Toshimi; (Kanagawa, JP) ; Tagami; Uno;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AJINOMOTO CO., INC. |
Tokyo |
|
JP |
|
|
Assignee: |
AJINOMOTO CO., INC.
Tokyo
JP
|
Family ID: |
49260189 |
Appl. No.: |
15/250056 |
Filed: |
August 29, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15133599 |
Apr 20, 2016 |
9453206 |
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15250056 |
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14491501 |
Sep 19, 2014 |
9347047 |
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15133599 |
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PCT/JP2013/059124 |
Mar 27, 2013 |
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14491501 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 2333/90616
20130101; C12P 13/06 20130101; C12P 13/08 20130101; G01N 33/6812
20130101; C12Q 1/32 20130101; C12Y 104/01009 20130101; C07K 2319/02
20130101; C12N 9/0016 20130101 |
International
Class: |
C12N 9/06 20060101
C12N009/06; C12P 13/08 20060101 C12P013/08; C12P 13/06 20060101
C12P013/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 30, 2012 |
JP |
2012-082777 |
Claims
1. A method of producing a derivative of a branched-chain amino
acid, comprising producing the derivative from the branched-chain
amino acid using a modified leucine dehydrogenase enzyme, wherein
said modified leucine dehydrogenase enzyme comprises at least one
amino acid mutation as compared to a non-modified leucine
dehydrogenase enzyme, wherein said modified leucine dehydrogenase
is improved in one or more properties selected from the group
consisting of: (a) substrate specificities for L-leucine,
L-isoleucine and L-valine; (b) activity for any branched-chain
amino acid; (c) thermal stability, and (d) combinations thereof,
wherein said modified leucine dehydrogenase is selected from the
group consisting of: (A) a protein comprising an amino acid
sequence of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, or SEQ ID NO:
8, but having a substitution of isoleucine in the TGI motif with an
amino acid selected from the group consisting of methionine,
arginine, histidine, phenylalanine, leucine, lysine, cysteine,
tyrosine, alanine, glycine, serine, asparagine, and tryptophan, (B)
a protein comprising an amino acid sequence of SEQ ID NO: 2, SEQ ID
NO: 4, SEQ ID NO: 6, or SEQ ID NO: 8, but having a substitution of
isoleucine in the GVI motif with an amino acid selected from the
group consisting of phenylalanine, histidine, asparagine, tyrosine,
leucine, lysine, glutamine, arginine, aspartic acid, threonine,
glutamic acid, serine, cysteine, alanine, glycine, valine,
tryptophan, and methionine, (C) a protein comprising an amino acid
sequence of SEQ ID NO: 2, SEQ ID NO: 4, SEQ ID NO: 6, or SEQ ID NO:
8, but having a substitution of isoleucine in the TGI motif with an
amino acid selected from the group consisting of methionine,
arginine, histidine, phenylalanine, leucine, lysine, cysteine,
tyrosine, alanine, glycine, serine, asparagine, and tryptophan, and
a substitution of isoleucine in the GVI motif with an amino acid
selected from the group consisting of phenylalanine, histidine,
asparagine, tyrosine, leucine, lysine, glutamine, arginine,
aspartic acid, threonine, glutamic acid, serine, cysteine, alanine,
glycine, valine, tryptophan, and methionine, and (D) a protein as
described in (A), (B), or (C) above, but also comprising one to ten
additional mutations of amino acid residues.
Description
[0001] This application is a divisional of, and claims priority
under 35 U.S.C. .sctn.120 to, U.S. patent application Ser. No.
15/133,599, filed Apr. 20, 2016, which was a divisional of, and
claimed priority under 35 U.S.C. .sctn.120 to, U.S. patent
application Ser. No. 14/491,501, filed Sep. 19, 2014, which was a
continuation of, and claimed priority under 35 U.S.C. .sctn.120 to,
International Patent Application No. PCT/JP2013/059124, filed on
Mar. 27, 2013, which claimed priority therethrough under 35 U.S.C.
.sctn.119 to Japanese Patent Application No. 2012-082777, filed on
Mar. 30, 2012, which are incorporated in their entireties by
reference. Also, the Sequence Listing filed electronically herewith
is hereby incorporated by reference (File name:
2016-08-29T_US-522D2_Seq_List; File size: 20 KB; Date recorded:
Aug. 29, 2016).
FIELD OF THE INVENTION
[0002] The present invention related to a modified leucine
dehydrogenase, a method of analyzing total branched-chain amino
acids using the same, and the like.
BRIEF DESCRIPTION OF THE RELATED ART
[0003] It is known that some amino acids can become indicators for
various health conditions. In particular, branched-chain amino
acids (BCAA: L-leucine, L-isoleucine and L-valine) are important
amino acids that are abundant in various biological samples, foods,
and beverages. The branched-chain amino acids are abundant in
muscle in living bodies and are known as a marker of protein
nutrition. It is known that concentrations of the branched-chain
amino acids in blood are reduced in patients with hepatic cirrhosis
or hepatic encephalopathy, and indicators such as Fisher ratio and
BTR value are utilized for health condition and follow-up of the
liver.
[0004] Methods using analytical instruments, including
high-performance liquid chromatography (HPLC) and LC-MS, are widely
used to analyze amino acids. When measuring total branched-chain
amino acids, an enzymatic kit for measuring the BTR value utilizing
leucine dehydrogenase (e.g., Japanese patent application laid-open
publication no. JP 2007-289096-A) and a biosensor for
electrochemically measuring the total branched-chain amino acids
utilizing leucine dehydrogenase (e.g., International Publication
no. WO2005/075970) have been reported.
SUMMARY OF THE INVENTION
[0005] There are several points that could be improved in the
measurement of concentrations of the total branched-chain amino
acids using a leucine dehydrogenase.
[0006] For example, concentration of the total branched-chain amino
acids is measured using a leucine dehydrogenase in an enzymatic
kit. However, these methods typically are performed until an
endpoint is reached at which the substrates are fully and
completely reacted. This is because substrate specificities
(reaction rates) of the leucine dehydrogenase for L-leucine,
L-isoleucine and L-valine are each different. For wild-type leucine
dehydrogenase, the substrate specificities for L-isoleucine and
L-valine are lower than that for L-leucine and therefore the
reaction rates for L-isoleucine and L-valine are slower than that
for L-leucine. Therefore, existing methods have the disadvantage
that it takes a long time to measure the concentration of the total
branched-chain amino acids in the enzymatic kit using the leucine
dehydrogenase due to the longer reaction rates of L-isoleucine and
L-valine.
[0007] In addition, when a plurality of amino acids that are the
substrates of the leucine dehydrogenase are present, each
concentration of branched-chain amino acids cannot be independently
measured with the biosensor. This is because the leucine
dehydrogenase reacts not only with L-leucine but also with
L-isoleucine and L-valine. In the case as above, a total
concentration of the branched-chain amino acids could also not be
measured in general. This is because the substrate specificities
(reaction rates) of the leucine dehydrogenase for L-leucine,
L-isoleucine and L-valine are different from each other.
[0008] As a result of an extensive study, the present inventors
have conceived that a concentration of total branched-chain amino
acids may be measured utlizing a rating method (initial rate
method) by enhancing an activity of a leucine dehydrogenase for
each amino acid of branched-chain amino acids, particularly for
L-isoleucine and L-valine, or the like, to improve substrate
specificities of the leucine dehydrogenase for the branched-chain
amino acids, in order to rapidly measure the concentration of the
total branched-chain amino acids, and have succeeded in developing
a modified leucine dehydrogenase that has improved substrate
specificities for the branched-chain amino acids. The present
inventors have also succeeded in improving other properties of the
leucine dehydrogenase that are associated with the measurement of
the concentration of the total branched-chain amino acids.
[0009] It is an aspect of the present invention to provide a
modified leucine dehydrogenase enzyme comprising at least one amino
acid mutation as compared to a non-modified leucine dehydrogenase
enzyme, wherein said modified leucine dehydrogenase is improved in
one or more properties selected from the group consisting of:
[0010] (a) substrate specificities for total branched-chain amino
acids;
[0011] (b) activity for any branched-chain amino acid;
[0012] (c) thermal stability; and
[0013] (d) combinations thereof.
[0014] It is a further aspect of the present invention to provide
the modified leucine dehydrogenase enzyme as described above,
wherein the mutation is a substitution of isoleucine in a TGI motif
in an amino acid sequence of the non-modified leucine dehydrogenase
enzyme.
[0015] It is a further aspect of the present invention to provide
the modified leucine dehydrogenase enzyme as described above,
wherein the isoleucine in the TGI motif is substituted with an
amino acid selected from the group consisting of methionine,
arginine, histidine, phenylalanine, leucine, lysine, cysteine,
tyrosine, alanine, glycine, serine, asparagine, and tryptophan.
[0016] It is a further aspect of the present invention to provide
the modified leucine dehydrogenase enzyme as described above,
wherein the mutation is a substitution of isoleucine in a GVI motif
in an amino acid sequence of the non-modified leucine dehydrogenase
enzyme.
[0017] It is a further aspect of the present invention to provide
the modified leucine dehydrogenase enzyme as described above,
wherein the isoleucine in the GVI motif is substituted with an
amino acid selected from the group consisting of phenylalanine,
histidine, asparagine, tyrosine, leucine, lysine, glutamine,
arginine, aspartic acid, threonine, glutamic acid, serine,
cysteine, alanine, glycine, valine, tryptophan, and methionine.
[0018] It is a further aspect of the present invention to provide
the modified leucine dehydrogenase enzyme as described above,
wherein the non-modified leucine dehydrogenase enzyme is derived
from Geobacillus stearothermophilus.
[0019] It is a further aspect of the present invention to provide
the modified leucine dehydrogenase enzyme as described above,
comprising a protein selected from the group consisting of:
[0020] (A) a protein comprising the amino acid sequence of SEQ ID
NO: 2, but having a substitution of isoleucine in the TGI motif
with an amino acid residue selected from the group consisting of
methionine, arginine, histidine, phenylalanine, leucine, lysine,
cysteine, tyrosine, alanine, glycine, serine, asparagine, or
tryptophan;
[0021] (B) a protein comprising the amino acid sequence of SEQ ID
NO: 2, but having a substitution of isoleucine in the GVI motif
with an amino acid selected from the group consisting of
phenylalanine, histidine, asparagine, tyrosine, leucine, lysine,
glutamine, arginine, aspartic acid, threonine, glutamic acid,
serine, cysteine, alanine, glycine, valine, tryptophan, and
methionine;
[0022] (C) a protein comprising the amino acid sequence of SEQ ID
NO: 2, but having a substitution of isoleucine in the TGI motif
with an amino acid selected from the group consisting of
methionine, arginine, histidine, phenylalanine, leucine, lysine,
cysteine, tyrosine, alanine, glycine, serine, asparagine, and
tryptophan, and a substitution of isoleucine in the GVI motif with
an amino acid selected from the grouop consisting of phenylalanine,
histidine, asparagine, tyrosine, leucine, lysine, glutamine,
arginine, aspartic acid, threonine, glutamic acid, serine,
cysteine, alanine, glycine, valine, tryptophan, and methionine,
and
[0023] (D) a protein as described in (A), (B), or (C) above, but
also comprising one or several additional mutations of amino acid
residues, and having one or more improved properties selected from
the group consisting of:
[0024] (a) substrate specificities for total branched-chain amino
acids;
[0025] (b) activity for any branched-chain amino acid; and
[0026] (c) thermal stability.
[0027] It is a further aspect of the present invention to provide a
method of analyzing total branched-chain amino acids, comprising
measuring the total branched-chain amino acids contained in a test
sample using the modified leucine dehydrogenase enzyme as described
above.
[0028] It is a further aspect of the present invention to provide
the method as described above, comprising mixing the test sample
with nicotinamide adenine dinucleotide (NAD.sup.+) and detecting
NADH formed from NAD.sup.+ by an action of the modified leucine
dehydrogenase enzyme.
[0029] It is a further aspect of the present invention to provide a
method of producing a derivative of a branched-chain amino acid,
comprising forming the derivative from the branched-chain amino
acid using the modified leucine dehydrogenase enzyme as described
above.
[0030] It is a further aspect of the present invention to provide a
polynucleotide encoding the modified leucine dehydrogenase enzyme
as described above.
[0031] It is a further aspect of the present invention to provide
an expression vector comprising the polynucleotide as described
above.
[0032] It is a further aspect of the present invention to provide a
transformant comprising the expression vector as described
above.
[0033] It is a further aspect of the present invention to provide a
method of producing a modified enzyme in which at least one amino
acid residue is mutated so as to improve a property of a leucine
dehydrogenase which is associated with measurement of total
branched-chain amino acids, comprising forming the modified enzyme
using the transformant as described above.
[0034] It is a further aspect of the present invention to provide a
kit for analyzing total branched-chain amino acids, comprising the
modified enzyme as described above.
[0035] It is a further aspect of the present invention to provide
the kit for as described above, further comprising at least one of
a buffer solution or a buffer salt for a reaction and nicotinamide
adenine dinucleotide (NAD.sup.+).
[0036] It is a further aspect of the present invention to provide
an enzyme sensor for analyzing total branched-chain amino acids,
comprising (a) an electrode for detection and (b) the modified
leucine dehydrogenase enzyme as described above, which is
immobilized or retained on the electrode for detection.
[0037] The modified enzyme of the present invention is useful for
rapid measurement of concentration of total branched-chain amino
acids with improved substrate specificity. The modified enzyme of
the present invention is also useful for measurement of any
branched-chain amino acid and/or production of derivatives of any
branched-chain amino acid (e.g., 2-oxo-derivative) because its
activity for the branched-chain amino acids is enhanced. The
modified enzyme of the present invention is also excellent in
stability because it is excellent in thermal stability in an
aqueous solution. Therefore the modified enzyme of the present
invention is useful particularly as a liquid reagent. The analysis
method of the present invention is useful for diagnosis of diseases
such as hepatic cirrhosis, hepatic encephalopathy, and the
like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 shows substrate specificities of each wild-type
leucine dehydrogenase for each branched-chain amino acid
(L-leucine, L-isoleucine and L-valine);
[0039] FIG. 2 shows changes of absorbance with time (means of n=3)
when each branched-chain amino acid (L-leucine, L-isoleucine and
L-valine) was reacted with a wild-type enzyme or the modified
enzyme I136R;
[0040] FIG. 3 shows activities of the wild-type enzyme or the
modified enzyme I136R for each branched-chain amino acid
(L-leucine, L-isoleucine and L-valine) at various concentration as
changes of absorbance (means of n=3) and showing standard curves
prepared from those values; and
[0041] FIG. 4 shows concentrations of total BCAA (means of n=3) in
plasma samples from rats measured by an enzymatic method and an
amino acid analyzer.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0042] The present invention provides a modified enzyme. The
modified enzyme of the present invention can be one in which at
least one amino acid residue in a leucine dehydrogenase is mutated
so as to improve a property of the leucine dehydrogenase, which is
associated with the measurement of total branched-chain amino
acids.
[0043] Examples of the mutation of the amino acid residue may
include substitution, deletion, addition and insertion, and the
substitution is preferred particular example.
[0044] Amino acid residues to be mutated include L-alanine (A),
L-asparagine (N), L-cysteine (C), L-glutamine (Q), glycine (G),
L-isoleucine (I), L-leucine (L), L-methionine (M), L-phenylalanine
(F), L-proline (P), L-serine (S), L-threonine (T), L-tryptophan
(W), L-tyrosine (Y), L-valine (V), L-aspartic acid (D), L-glutamic
acid (E), L-arginine (R), L-histidine (H) or L-lysine (K), and may
be a naturally occurring L-.alpha.-amino acid. When the mutation is
substitution, addition or insertion, the amino acid residue to be
substituted, added or inserted can be the same as the amino acid
residue to be mutated as described above.
[0045] The branched-chain amino acids ("BCAA") include naturally
occurring L-.alpha.-amino acids having a branched chain as a side
chain, and specifically include L-leucine, L-isoleucine, and
L-valine. The branched-chain amino acids (i.e., L-leucine,
L-isoleucine and L-valine) are collectively measured in the
measurement of the total branched-chain amino acids.
[0046] The leucine dehydrogenase is an oxidoreductase that
catalyzes the following reaction (EC 1.4.1.9).
L-leucine+H.sub.2O+NAD.sup.+.fwdarw.4-methyl-2-oxopentanoic
acid+NH.sub.3+NADH.sup.+
[0047] It is known that although a wild-type leucine dehydrogenase
acts upon not only L-leucine, but also on L-isoleucine and
L-valine; although its activities for L-isoleucine and L-valine are
lower than that for L-leucine. The substrate specificities of the
wild-type leucine dehydrogenases derived from Bacillus sp. and
Geobacillus stearothermophilus for L-leucine, L-isoleucine and
L-valine are shown in FIG. 1 as relative activities when the
relative activities for L-leucine are regarded as 100. As shown in
FIG. 1, the activities of the wild-type leucine dehydrogenases are
relatively low for the branched-chain amino acids other than
L-leucine, and in particular, the relative activities for
L-isoleucine are 75 or less relative to the activities for
L-leucine.
[0048] Wild-type leucine dehydrogenase derived from any organism,
such as microorganisms such as bacteria, actinomycetes and fungi,
as well as insects, fish, animals and plants, can be used to derive
the modified enzyme of the present invention. Examples of the
wild-type leucine dehydrogenase may include those derived from
organisms belonging to the genus Bacillus and genera related
thereto. Examples of the genera related to the genus Bacillus may
include the genus Geobacillus, the genus Paenibacillus and the
genus Oceanobacillus. The genera related to the genus Bacillus
belong to Bacillaceae, as is similar to the genus Bacillus.
[0049] Examples of the microorganisms belonging to the genus
Bacillus and the genera related thereto may include Bacillus
sphaericus, Bacillus cereus, Bacillus licheniformis, Bacillus sp.,
and Geobacillus stearothermophilus.
[0050] The position at which a mutation is introduced in the
wild-type leucine dehydrogenase can be a position located in close
proximity to an active center of the leucine dehydrogenase. A
person skilled in the art can align an amino acid sequence of the
leucine dehydrogenase derived from Geobacillus stearothermophilus
with an amino acid sequence of another leucine dehydrogenase, and
thus can easily determine an amino acid residue position located in
close proximity to an active center of the wild-type leucine
dehydrogenases derived from organisms other than Geobacillus
stearothermophilus.
[0051] In addition, results of analyzing three-dimensional
structures have been reported for leucine dehydrogenases (see,
e.g., Baker et al., Structure 3: 693-705 (1995)). Therefore, a
person skilled in the art can also easily specify the amino acid
residue located in close proximity of an active center of the
leucine dehydrogenases derived from organisms other than
Geobacillus stearothermophilus, based on the results of analyzing
three-dimensional structure.
[0052] In a particular embodiment, a mutation that results in the
improvement of the property of the leucine dehydrogenase associated
with the measurement of the total branched-chain amino acids can be
a substitution of isoleucine (I) in a TGI motif in the wild-type
leucine dehydrogenase. The TGI motif is composed of the three
consecutive amino acid residues threonine (T)-glycine
(G)-isoleucine (I). The position of the TGI motif in the amino acid
sequence of the wild-type leucine dehydrogenase may be different
depending on the origin of the enzyme. However, a person skilled in
the art can appropriately determine the position of the TGI motif
in the amino acid sequence of the wild-type leucine dehydrogenase,
and thus can specify the position of isoleucine (I) to be
substituted. Generally, in the amino acid sequence of the wild-type
leucine dehydrogenase, the TGI motif is located within an amino
acid region of positions 134 to 138 and the isoleucine (I) is
located at positions 136 to 138 (see, e.g., Table 1).
TABLE-US-00001 TABLE 1 Position of TGI motif in leucine
dehydrogenase SEQ ID NO (sequence of wild-type enzyme Position
Nucleotide Amino acid Leucine dehydrogenase TGI motif Ile sequence
sequence G. stearothermophilus 134-136 136 1 2 B. sphaericus
134-136 136 3 4 B. cereus 136-138 138 5 6 B. licheniformis 134-136
136 7 8
[0053] In another particular embodiment, a mutation that results in
the improvement of the property of the leucine dehydrogenase
associated with the measurement of the total branched-chain amino
acids is a substitution of isoleucine (I) in a GVI motif of the
wild-type leucine dehydrogenase. The GVI motif is composed of the
three consecutive amino acid residues of glycine (G)-valine
(V)-isoleucine (I). The position of the GVI motif in the amino acid
sequence of the wild-type leucine dehydrogenase may be different
depending on the origin of the enzyme. However, a person skilled in
the art can appropriately determine the position of the GVI motif
in the amino acid sequence of the wild-type leucine dehydrogenase,
and thus can specify the position of isoleucine (I) to be
substituted. Generally, in the amino acid sequence of the wild-type
leucine dehydrogenase, the GVI motif is located within an amino
acid region at positions 290 to 294, and isoleucine (I) is located
at positions 292 to 294 (see, e.g., Table 2). The modified enzyme
of the present invention may further have the above substitution of
isoleucine (I) in the TGI motif in addition to the substitution of
isoleucine (I) in the GVI motif as the mutations to improve the
property of the leucine dehydrogenase associated with the
measurement of the total branched-chain amino acids.
TABLE-US-00002 TABLE 2 Position of GVI motif in leucine
dehydrogenase SEQ ID NO (sequence of wild-type enzyme) Position
Nucleotide Amino acid Leucine dehydrogenase GVI motif Ile sequence
sequence G. stearothermophilus 290-292 292 1 2 B. sphaericus
290-292 292 3 4 B. cereus 292-294 294 5 6 B. licheniformis 290-292
292 7 8
[0054] The properties of the leucine dehydrogenase which are
associated with the measurement of the total branched-chain amino
acids may include the following:
[0055] (a) substrate specificities of the leucine dehydrogenase for
the total branched-chain amino acids;
[0056] (b) an activity of the leucine dehydrogenase for any
branched-chain amino acid; and
[0057] (c) a thermal stability of the leucine dehydrogenase.
[0058] The modified enzyme of the present invention may have only
one of the aforementioned properties, or may have two or three of
the aforementioned properties in combination.
[0059] For the isoleucine (I) in the TGI motif, examples of the
mutation to improve at least one property selected from the
properties (a) to (c) may include substitutions with methionine
(M), arginine (R), histidine (H), phenylalanine (F), leucine (L),
lysine (K), cysteine (C), tyrosine (Y), alanine (A), glycine (G),
serine (S), asparagine (N) and tryptophan (W).
[0060] For the isoleucine (I) in the GVI motif, examples of the
mutation to improve at least one property selected from the
properties (a) to (c) may include substitutions with phenylalanine
(F), histidine (H), asparagine (N), tyrosine (Y), leucine (L),
lysine (K), glutamine (Q), arginine (R), aspartic acid (D),
threonine (T), glutamic acid (E), serine (S), cysteine (C), alanine
(A), glycine (G), valine (V), tryptophan (W) and methionine
(M).
[0061] The modified enzyme of the present invention can be used
under any pH condition, and is suitably used under a neutral
condition and/or an alkaline condition.
[0062] The neutral condition under which the modified enzyme of the
present invention is suitably used can be any pH condition within
the range of pH 6.0 or higher and pH 8.0 or lower. For example, the
neutral condition can be any pH condition within the range of pH
7.0 or higher and pH 8.0 or lower (e.g., pH 7.0, pH 7.5 or pH
8.0).
[0063] The alkaline condition under which the modified enzyme of
the present invention is suitably used refers to any pH condition
within the range of more than pH 8.0 and pH 11.0 or lower. An upper
limit of a pH range in the alkaline condition can be 10.5 or lower
or even 10.0 or lower. For example, the alkaline condition can be
any pH condition within the range of pH 8.5 or higher and pH 9.5 or
lower (e.g., pH 9.0).
[0064] In one embodiment, the substrate specificities of leucine
dehydrogenase for the total branched-chain amino acids are improved
as the property of the leucine dehydrogenase which is associated
with the measurement of the total branched-chain amino acids. The
improvement of the substrate specificities of the leucine
dehydrogenase for the total branched-chain amino acids are not
intended to enhance the substrate specificity of the leucine
dehydrogenase for a certain branched-chain amino acid, but refers
to making the substrate specificities (reaction rates) for all of
the branched-chain amino acids (i.e., L-leucine, L-isoleucine and
L-valine) more equivalent. Specifically, the improvement of the
substrate specificities of the leucine dehydrogenase for the total
branched-chain amino acids can be accomplished when each relative
activity of the modified enzyme for isoleucine and valine is closer
to 100 compared to each relative activity of the wild-type enzyme
for isoleucine and valine, when the relative activity of the
leucine dehydrogenase for leucine is regarded as 100. Concerning
the substrate specificities of the leucine dehydrogenase for the
total branched-chain amino acids, the relative activities of the
leucine dehydrogenase for both isoleucine and valine can be 80 or
more and 120 or less, 85 or more and 115 or less, 90 or more and
110 or less, or even 95 or more and 105 or less when the relative
activity of the leucine dehydrogenase for leucine is regarded as
100. Examples of the modification in the modified enzyme of the
present invention in which the relative activities of the leucine
dehydrogenase for both isoleucine and valine are 80 or more and 120
or less when the relative activity for leucine is regarded as 100
may include 1) the substitution of isoleucine (I) in the TGI motif
with an amino acid residue described below and/or the substitution
of isoleucine (I) in the GVI motif with an amino acid residue
described below, which is suitable for the improvement of the
substrate specificities under the alkaline condition, as well as 2)
the substitution of isoleucine (I) in the TGI motif with an amino
acid residue described below and/or the substitution of isoleucine
(I) in the GVI motif with an amino acid residue described below,
which is suitable for the improvement of the property under the
neutral condition.
[0065] 1) Substitution Suitable for Improvement of Substrate
Specificities Under Alkaline Condition
[0066] (a) Amino acid residue after substitution at position 136
(alkaline condition)
[0067] Methionine (M), arginine (R), phenylalanine (F), lysine (K),
cysteine (C), tyrosine (Y), alanine (A), glycine (G) or serine
(S)
[0068] (b) Amino acid residue after substitution at position 292
(alkaline condition)
[0069] Phenylalanine (F), histidine (H), asparagine (N), tyrosine
(Y), lysine (K), glutamine (Q), glutamic acid (E) or glycine
(G)
[0070] 2) Substitution Suitable for Improvement of Substrate
Specificities Under Neutral Condition
[0071] (c) Amino acid residue after substitution at position 136
(neutral condition)
[0072] Alanine (A), glycine (G), histidine (H), lysine (K), leucine
(L), serine (S) or tyrosine (Y)
[0073] (d) Amino acid residue after substitution at position 292
(neutral condition)
[0074] Alanine (A), cysteine (C), aspartic acid (D), glycine (G),
lysine (K), leucine (L), methionine (M), arginine (R), serine (S),
threonine (T) or valine (V).
[0075] In another embodiment, the activity of the leucine
dehydrogenase for any branched-chain amino acid is improved as the
property of the leucine dehydrogenase which is associated with the
measurement of the total branched-chain amino acids. The
improvement of the activity of the leucine dehydrogenase for any
branched-chain amino acid means that the activity of the modified
enzyme for one or more amino acids such as L-leucine, L-isoleucine
and L-valine is enhanced relative to the activity of the wild-type
enzyme for the same. Specifically, the improvement of the activity
of the leucine dehydrogenase for any branched-chain amino acid can
be accomplished in the case where the activity of the modified
leucine dehydrogenase for any amino acid such as L-leucine,
L-isoleucine and L-valine is higher than 100 when the activity of
the wild-type leucine dehydrogenase for that amino acid is regarded
as 100. Such a modified enzyme enables rapid measurement of an
individual branched-chain amino acid, and consequently is useful
for the measurement of the total branched-chain amino acids. A
level of the enhancement of the activity of the modified enzyme can
be 1.3 fold or more, 1.5 fold or more, 1.7 fold or more, or even
2.0 fold or more relative to the activity of the wild-type enzyme.
Examples of the modification in the modified enzyme of the present
invention having 1.3 fold or more enhancement of the activity
relative to the wild-type enzyme may include 1) the substitution of
isoleucine (I) in the TGI motif with the following amino acid
residue and/or the substitution of isoleucine (I) in the GVI motif
with the following amino acid residue, which is suitable for the
improvement of the activity under the alkaline condition as well as
2) the substitution of isoleucine (I) in the TGI motif with the
following amino acid residue and/or the substitution of isoleucine
(I) in the GVI motif with the following amino acid residue, which
is suitable for the improvement of the activity under the neutral
condition.
[0076] 1) Substitution Suitable for Improvement of Activity Under
Alkaline Condition
[0077] 1-1) Amino Acid Residues after Substitution at Position 136
(Under Alkaline Condition)
[0078] (i) Enhancement of the Activity for L-Leucine (Under
Alkaline Condition)
[0079] Methionine (M), arginine (R), histidine (H), phenylalanine
(F), leucine (L), lysine (K), cysteine (C), tyrosine (Y), alanine
(A), glycine (G), serine (S), asparagine (N), or tryptophan
(W).
[0080] (ii) Enhancement of Activity for L-Isoleucine (Under
Alkaline Condition)
[0081] Methionine (M), arginine (R), histidine (H), phenylalanine
(F), leucine (L), lysine (K), cysteine (C), tyrosine (Y), alanine
(A), glycine (G), serine (S), asparagine (N), or tryptophan
(W).
[0082] (iii) Enhancement of Activity for L-Valine (Under Alkaline
Condition)
[0083] Methionine (M), arginine (R), histidine (H), phenylalanine
(F), leucine (L), lysine (K), cysteine (C), tyrosine (Y), alanine
(A), glycine (G), serine (S), asparagine (N), or tryptophan
(W).
[0084] 1-2) Amino Acid Residues after Substitution at Position 292
(Under Alkaline Condition)
[0085] (iv) Enhancement of Activity for L-Leucine (Under Alkaline
Condition)
[0086] Phenylalanine (F), histidine (H), asparagine (N), tyrosine
(Y), leucine (L), lysine (K), glutamine (Q), arginine (R), aspartic
acid (D), threonine (T), glutamic acid (E), serine (S), cysteine
(C), alanine (A), or glycine (G).
[0087] (v) Enhancement of Activity for L-Isoleucine (Under Alkaline
Condition)
[0088] Phenylalanine (F), histidine (H), asparagine (N), tyrosine
(Y), leucine (L), lysine (K), glutamine (Q), arginine (R), aspartic
acid (D), threonine (T), glutamic acid (E), serine (S), cysteine
(C), alanine (A), glycine (G), valine (V), or tryptophan (W).
[0089] (vi) Enhancement of Activity for L-Valine (Under Alkaline
Condition)
[0090] Phenylalanine (F), histidine (H), asparagine (N), tyrosine
(Y), leucine (L), lysine (K), glutamine (Q), arginine (R), aspartic
acid (D), threonine (T), glutamic acid (E), serine (S), cysteine
(C), alanine (A), glycine (G), or valine (V).
[0091] 2) Substitutions Suitable for Improvement of Activity Under
Neutral Condition
[0092] 2-1) Amino Acid Residues after Substitution at Position 136
(Under Neutral Condition)
[0093] (i') Enhancement of Activity for L-Leucine (Under Neutral
Condition)
[0094] Alanine (A), cysteine (C), phenylalanine (F), glycine (G),
histidine (H), lysine (K), leucine (L), methionine (M), asparagine
(N), arginine (R), serine (S), tryptophan (W), or tyrosine (Y).
[0095] (ii') Enhancement of Activity for L-Isoleucine (Under
Neutral Condition)
[0096] Alanine (A), cysteine (C), phenylalanine (F), glycine (G),
histidine (H), lysine (K), leucine (L), methionine (M), asparagine
(N), arginine (R), serine (S), tryptophan (W), or tyrosine (Y).
[0097] (iii') Enhancement of Activity for L-Valine (Under Neutral
Condition)
[0098] Alanine (A), cysteine (C), phenylalanine (F), glycine (G),
histidine (H), lysine (K), leucine (L), methionine (M), asparagine
(N), glutamine (Q), arginine (R), serine (S), tryptophan (W), or
tyrosine (Y).
[0099] 2-2) Amino Acid Residues after Substitution at Position 292
(Under Neutral Condition)
[0100] (iv') Enhancement of Activity for L-Leucine (Under Neutral
Condition)
[0101] Alanine (A), cysteine (C), aspartic acid (D), glutamic acid
(E), phenylalanine (F), glycine (G), histidine (H), lysine (K),
leucine (L), methionine (M), asparagine (N), glutamine (Q),
arginine (R), serine (S), threonine (T), valine (V), tryptophan
(W), or tyrosine (Y).
[0102] (v') Enhancement of Activity for L-Isoleucine (Under Neutral
Condition)
[0103] Alanine (A), cysteine (C), aspartic acid (D), glutamic acid
(E), phenylalanine (F), glycine (G), histidine (H), lysine (K),
leucine (L), methionine (M), asparagine (N), glutamine (Q),
arginine (R), serine (S), threonine (T), tryptophan (W), or
tyrosine (Y).
[0104] (vi') Enhancement of Activity for L-Valine (Under Neutral
Condition)
[0105] Alanine (A), cysteine (C), aspartic acid (D), glutamic acid
(E), phenylalanine (F), glycine (G), histidine (H), lysine (K),
leucine (L), methionine (M), asparagine (N), glutamine (Q),
arginine (R), serine (S), threonine (T), valine (V), tryptophan
(W), or tyrosine (Y).
[0106] In still another embodiment, the thermal stability of the
leucine dehydrogenase is improved as the property of the leucine
dehydrogenase which is associated with the measurement of the total
branched-chain amino acids. The improvement of the thermal
stability of the leucine dehydrogenase means that the thermal
stability of the modified enzyme is further enhanced relative to
that of the wild-type enzyme. Specifically, the improvement of the
thermal stability of the leucine dehydrogenase can be accomplished
when a remaining activity of the modified enzyme is higher than
that of the wild-type enzyme when the enzyme is treated in an
aqueous solution at 60.degree. C. for one hour. A thermal stability
test of the leucine dehydrogenase in the aqueous solution can have
significance as an acceleration test for evaluating the stability
(particularly liquid stability) of the leucine dehydrogenase.
Therefore, when the thermal stability of the modified enzyme in the
aqueous solution is high, the stability (particularly liquid
stability) of the modified enzyme also tends to be high. An enzyme
showing high liquid stability can be stored in a liquid form for a
long period of time, and thus, such a modified enzyme is useful as
a liquid reagent for the measurement of the total branched-chain
amino acids. A level of the enhancement of the thermal stability of
the modified enzyme can be 1.1 fold or more or 1.2 fold or more
relative to that of the wild-type enzyme. Examples of the
modification in the modified enzyme of the present invention having
1.1 fold or more enhanced thermal stability relative to the
wild-type enzyme may include the substitution of isoleucine (I) in
the TGI motif with the following amino acid residue and/or the
substitution of isoleucine (I) in the GVI motif with the following
amino acid residue.
[0107] Amino acid residues after substitution at position 136
[0108] Methionine (M), arginine (R), phenylalanine (F), or lysine
(K).
[0109] Amino acid residues after substitution at position 292
[0110] Phenylalanine (F)
[0111] The modified enzyme of the present invention may also have
another peptide component (e.g., a tag moiety) at the C-terminus or
N-terminus. Examples of the other peptide component that can be
added to the modified enzyme of the present invention may include
peptide components that make purification of the objective protein
easy (e.g., tag moiety such as histidine tag and strep-tag II;
proteins such as glutathione-S-transferase and maltose-binding
protein commonly used for the purification of the objective
protein), peptide components that enhance solubility of the
objective protein (e.g., Nus-tag), peptide components that work as
a chaperon (e.g., trigger factor), and peptide components as a
protein or a domain of the protein having another function or a
linker connecting them.
[0112] The modified enzyme of the present invention may also have
supplemental mutations (e.g., substitutions, deletions, insertions
and additions) of one or several amino acid residues in an amino
acid sequence of the leucine dehydrogenase having the above
mutation(s) as long as the aforementioned property is retained. The
number of amino acid residues in which the supplemental mutation
can be introduced are, for example, 1 to 100, 1 to 50, 1 to 40, 1
to 30 or even 1 to 20 or 1 to 10 (e.g., 1, 2, 3, 4 or 5). A person
skilled in the art can appropriately make such a modified enzyme
retaining the aforementioned property.
[0113] Therefore, the modified enzyme of the present invention may
be the following (i) or (ii):
[0114] a protein having an amino acid sequence having a mutation or
mutations (e.g., substitution) of isoleucine (I) in the TGI motif
and/or isoleucine (I) in the GVI motif in an amino acid sequence of
the leucine dehydrogenase, and having the improved property of the
leucine dehydrogenase which is associated with the measurement of
total branched-chain amino acids; or
[0115] a protein having an amino acid sequence having a
supplemental mutation of one or several amino acid residues in the
amino acid sequence having a mutation or mutations (e.g.,
substitution) of isoleucine (I) in the TGI motif and/or isoleucine
(I) in the GVI motif in the amino acid sequence of the leucine
dehydrogenase, and having the improved property of the leucine
dehydrogenase which is associated with the measurement of the total
branched-chain amino acids.
[0116] The modified enzyme of the present invention may also be
that having an amino acid sequence having at least 90% or more
sequence identity to the amino acid sequence of the (wild-type)
leucine dehydrogenase before its mutation because of having both
the aforementioned mutation or mutations and the supplemental
mutation or mutations. A percentage of the amino acid sequence
identity may be 92% or more, 95% or more, 97% or more, or 98% or
more or 99% or more.
[0117] The identity between the amino acid sequences can be
determined, for example, using algorithm BLAST by Karlin and
Altschul (Pro. Natl. Acad. Sci. USA, 90, 5873 (1993)) and FASTA by
Pearson (MethodsEnzymol., 183, 63 (1990)). A program referred to as
BLASTP has been developed based on this algorithm BLAST (see
www.ncbi.nlm.nih.gov). Thus, the identity between the amino acid
sequences may be calculated using these programs with the default
setting. Also, for example, a numerical value obtained by
calculating similarity as a percentage using a full length
polypeptide portion encoded in an ORF and using software GENETYX
Ver. 7.09 with setting of Unit Size to Compare=2 from Genetyx
Corporation employing Lipman-Pearson method may be used as the
identity between the amino acid sequences. The lowest value among
the values derived from these calculations may be employed as the
identity between the amino acid sequences.
[0118] The position of an amino acid residue at which the
supplemental mutation can be introduced in an amino acid sequence
would be apparent to a person skilled in the art. For example, the
supplemental mutation can be introduced with reference to an
alignment of the amino acid sequence. Specifically, a person
skilled in the art can (1) compare amino acid sequences of a
plurality of homologs (e.g., an amino acid sequence represented by
SEQ ID NO:2 and an amino acid sequence of the other homolog(s)),
(2) demonstrate relatively conserved regions and relatively not
conserved regions, then (3) predict regions capable of playing a
functionally important role and regions incapable of playing a
functionally important role from the relatively conserved regions
and the relatively not conserved regions, respectively, and thus
recognize correlativity between a structure and a function. The
analysis result of the three-dimensional structure has been
reported for leucine dehydrogenases as described above. Thus, a
person skilled in the art can introduce the supplemental mutation
based on the analysis result of the three-dimensional structure so
as to enable the retention of the aforementioned property.
[0119] When the supplemental mutation of the amino acid residue is
a substitution, such a substitution of the amino acid residue may
be a conservative substitution. The term "conservative
substitution" refers to substituting a given amino acid residue
with an amino acid residue having a similar side chain. Families of
the amino acid residues having the similar side chain are
well-known in the art. Examples of such families may include amino
acids having a basic side chain (e.g., lysine, arginine,
histidine), amino acids having an acidic side chain (e.g., aspartic
acid, glutamic acid), amino acids having an uncharged polar side
chain (e.g., asparagine, glutamine, serine, threonine, tyrosine,
cysteine), amino acids having a nonpolar side chain (e.g., glycine,
alanine, valine, leucine, isoleucine, proline, phenylalanine,
methionine, tryptophan), amino acids having a branched side chain
at position .beta. (e.g., threonine, valine, isoleucine), amino
acids having an aromatic side chain (e.g., tyrosine, phenylalanine,
tryptophan, histidine), amino acids having a side chain containing
a hydroxyl (e.g., alcoholic, phenolic) group (e.g., serine,
threonine, tyrosine), and amino acids having a sulfur-containing
side chain (e.g., cysteine, methionine). For example, the
conservative substitution of the amino acid may be the substitution
between aspartic acid and glutamic acid, the substitution between
arginine, lysine and histidine, the substitution between tryptophan
and phenylalanine, the substitution between phenylalanine and
valine, the substitution between leucine, isoleucine and alanine,
and the substitution between glycine and alanine.
[0120] The modified enzyme of the present invention can be prepared
using a transformant of the present invention, which expresses the
modified enzyme of the present invention or a cell-free system. The
transformant of the present invention can be made, for example, by
making an expression vector for the modified enzyme of the present
invention and introducing this expression vector into a host. For
example, the transformant of the present invention can be obtained
by making the expression vector in which the polynucleotide of the
present invention has been incorporated and introducing this vector
into an appropriate host. Various prokaryotic cells including cells
from bacteria belonging to genera Escherichia (e.g., Escherichia
coli), Corynebacterium (e.g., Corynebacterium glutamicum) and
Bacillus (e.g., Bacillus subtilis), and various eukaryotic cells
including cells from fungi belonging to genera Saccharomyces (e.g.,
Saccharomyces cerevisiae), Pichia (e.g., Pichia stipitis) and
Aspergillus (e.g., Aspergillus oryzae) can be used as the host for
expressing the modified enzyme of the present invention. A strain
in which a certain gene has been deleted may be used as the host.
Examples of the transformant may include transformants in which the
vector is retained in its cytoplasm and transformants in which an
objective gene is integrated into its genome.
[0121] The transformant of the present invention can be cultured in
a medium having a composition described later using a given culture
apparatus (e.g., test tube, flask, jar fermenter). A culture
condition can appropriately be determined. Specifically, a culture
temperature may be 25 to 37.degree. C., a pH value may be 6.5 to
7.5, and a culture period may be 1 to 100 hours. Cultivation may
also be carried out by managing the dissolved oxygen concentration.
In this case, the dissolved oxygen concentration (DO value) may be
used as an indicator for control. A ventilation/stirring condition
can be controlled so that the relative dissolved oxygen
concentration, the DO value, does not fall below 1 to 10% for
example, or not below 3 to 8% when an oxygen concentration in the
air is 21%. The cultivation may be a batch cultivation or a
fed-batch cultivation. In the case of the fed-batch cultivation,
the cultivation can also be continued by sequentially adding
continuously or discontinuously a solution as a sugar source and a
solution containing phosphoric acid to the culture medium.
[0122] The host to be transformed is as described above, and can be
Escherichia coli, or the host can be Escherichia coli K12
subspecies Escherichia coli JM109 strain, DH5.alpha. strain, HB101
strain, BL21 (DE3) strain, and the like. Methods of performing the
transformation and methods of selecting the transformant have been
described in Molecular Cloning: A Laboratory Manual, 3rd edition,
Cold Spring Harbor press (2001 Jan. 15), and the like. Hereinafter,
a method of making transformed Escherichia coli and producing a
predetermined enzyme using this will be described specifically by
way of example only.
[0123] A promoter used for producing a foreign protein in E. coli
can generally be used as a promoter for expressing the
polynucleotide of the present invention. Examples thereof may
include potent promoters such as a PhoA, PhoC, T7 promoter, a lac
promoter, a trp promoter, a trc promoter, a tac promoter, PR and PL
promoters of lambda phage, and a T5 promoter, and the PhoA, PhoC
and lac promoters are preferred. For example, pUC (e.g., pUC19,
pUC18), pSTV, pBR (e.g., pBR322), pHSG (e.g., pHSG299, pHSG298,
pHSG399, pHSG398), RSF (e.g., RSF1010), pACYC (e.g., pACYC177,
pACYC184), pMW (e.g., pMW119, pMW118, pMW219, pMW218), pQE (e.g.,
pQE30) and derivatives thereof may be used as a vector. A vector
from phage DNA may also be utilized as the other vector. Further,
an expression vector that includes a promoter and can express an
inserted DNA sequence may also be used. Preferably, the vector may
be pUC, pSTV, or pMW.
[0124] Also, a terminator that is a transcription terminating
sequence may be ligated downstream of the polynucleotide of the
present invention. Examples of such a terminator may include a T7
terminator, an fd phage terminator, a T4 terminator, a terminator
of a tetracycline resistant gene, and a terminator of Escherichia
coli trpA gene.
[0125] The vector for introducing the polynucleotide of the present
invention into Escherichia coli can be a so-called multicopy type,
and examples thereof may include plasmids which have an replication
origin from ColEl, such as pUC-based plasmids, pBR322-based
plasmids and derivatives thereof. Here the "derivative" means those
in which the modification has been given to the plasmid by
substitution, deletion, insertion and/or addition of base(s). The
"modification" referred to herein also includes modification by
mutagenesis using a mutating agent, UV irradiation or the like, or
naturally occurring mutations.
[0126] In order to select the transformant, the vector can have a
marker such as an ampicillin resistant gene. Expression vectors
having a potent promoter are commercially available as such a
plasmid (e.g., pUC-based (supplied from Takara Bio Inc.),
pPROK-based (supplied from Clontech), pKK233-2-based (supplied from
Clontech)).
[0127] The modified enzyme of the present invention can be obtained
by transforming Escherichia coli using the resulting expression
vector of the present invention and culturing this Escherichia
coli.
[0128] Media such as M9/casamino acid medium and LB medium
generally used for culturing Escherichia coli may be used as the
medium. The medium may contain a predetermined carbon source,
nitrogen source, and coenzyme (e.g., pyridoxine hydrochloride).
Specifically, peptone, yeast extract, NaCl, glucose, MgSO.sub.4,
ammonium sulfate, potassium dihydrogen phosphate, ferric sulfate,
manganese sulfate, and the like may be used. A cultivation
condition and a production inducing condition are appropriately
selected depending on types of a marker and a promoter in a vector
and a host to be used.
[0129] The modified enzyme of the present invention can be
recovered by the following methods. The modified enzyme of the
present invention can be obtained as a pulverized or lysed product
by collecting the transformant of the present invention and
subsequently pulverizing (e.g., sonication or homogenization) or
lysing (e.g., treatment with lysozyme) the microbial cells. The
modified enzyme of the present invention can be obtained by
subjecting such a pulverized or lysed product to techniques such as
extraction, precipitation, filtration, and column
chromatography.
[0130] The present invention also provides a method of analyzing
the total branched-chain amino acids. The analysis method of the
present invention can include the steps of measuring the total
branched-chain amino acids contained in a test sample using the
modified enzyme of the present invention.
[0131] The test sample is not particularly limited as long as the
sample is suspected of containing any branched-chain amino acid
(preferably the total branched-chain amino acids), and examples
thereof may include biological samples (e.g., blood, urine, saliva,
tear, and the like) and food and beverage (e.g., nutrient drinks
and amino acid beverages).
[0132] The analysis method of the present invention is not
particularly limited as long as the total branched-chain amino
acids can be measured using the modified enzyme of the present
invention. For example, the total branched-chain amino acids can be
measured by mixing the test sample with nicotinamide adenine
dinucleotide (NAD.sup.+) under the alkaline condition or the
neutral condition, preferably in alkaline buffer, then subjecting
the mixed sample to an enzymatic reaction using the modified enzyme
of the present invention, and finally detecting NADH formed from
NAD.sup.+ by the action of the modified enzyme of the present
invention. Specifically, by allowing the modified enzyme to act
upon the test sample in the alkaline buffer in the presence of
nicotinamide adenine dinucleotide (NAD.sup.+), the reduced form
(NADH) is generated from nicotinamide adenine dinucleotide
(NAD.sup.+) while an amino group of a substrate contained in the
biological sample is oxidatively deaminated. Thus, the total
branched-chain amino acids can be quantified by detecting NADH by
an absorbance (340 nm) or the like. The methods of measuring the
amino acid by such a methodology are known (see e.g., Ueatrongchit
T, Asano Y, Anal Biochem., 2011 Mar. 1; 410(1): 44-56). The total
branched-chain amino acids can also be quantified by reducing a dye
with the formed NADH and detecting color development of the reduced
dye as an absorbance or the like. Further, NADH can also be
detected by an electrochemical technique. For example, it is
possible to measure the total branched-chain amino acids by
electrochemically oxidizing NADH formed by allowing the modified
enzyme to act upon the test sample under the alkaline or neutral
condition and measuring its oxidation electric current, or by
reducing a coexisting electronic mediator by the formed NADH and
measuring oxidation electric current when the reduced electronic
mediator is electrochemically oxidized. An electronic transfer
between the NADH and the electronic mediator may be mediated by a
catalyst. The total branched-chain amino acids can be measured by
the rating method (initial rate method).
[0133] The modified enzyme of the present invention is not reacted
with amino acids other than the branched-chain amino acids or has a
low reactivity therewith. Therefore, even when not only the
branched-chain amino acids but also other amino acids are contained
in a test sample, an amount of the branched-chain amino acids in
the test sample can be evaluated by using the modified enzyme of
the present invention.
[0134] Further, the present invention includes a kit for analyzing
the total branched-chain amino acids including the modified enzyme
of the present invention.
[0135] The kit of the present invention can further include at
least one of a buffer solution or a buffer salt for a reaction and
nicotinamide adenine dinucleotide (NAD.sup.+).
[0136] The buffer solution or the buffer salt for the reaction is
used for keeping a pH value in a reaction solution suitable for an
objective enzymatic reaction. The buffer solution or the buffer
salt for the reaction is alkaline or neutral, and preferably
alkaline.
[0137] When the kit of the present invention includes nicotinamide
adenine dinucleotide (NAD.sup.+), the kit of the present invention
may further include a dye to be reduced by NADH. In this case, the
dye is reduced by NADH formed from NAD.sup.+ by an action of the
modified enzyme of the present invention, and the color development
from the reduced dye can be detected by the absorbance and the
like. A substance working as an electronic mediator may be involved
in the reduction of the dye.
[0138] The present invention also provides an enzyme sensor for
analyzing the branched-chain amino acid including (a) an electrode
for detection and (b) the modified enzyme of the present invention
immobilized or retained on the electrode for detection. The
modified enzyme of the present invention is immobilized or retained
on the electrode directly or indirectly.
[0139] It is possible to use, for example, a biosensor that
directly or indirectly detects a product or a byproduct
(NH.sub.3+NADH+H.sup.+) formed form the total branched-chain amino
acids by the modified enzyme of the present invention as the
electrode for detection. More specifically, examples of the
electrode for detection include an electrode for detection
utilizing the modified enzyme of the present invention and
nicotinamide adenine dinucleotide (NAD.sup.+). Those described in
International Publication No. WO2005/075970 and International
Publication No. WO00/57166 or others can be used as such an
electrode for detection.
EXAMPLES
[0140] The present invention will be described in detail with
reference to following Examples, but the present invention is not
limited thereto.
[0141] Enzymatic Quantification Method
[0142] In an enzymatic quantification method for L-leucine,
L-isoleucine and L-valine, leucine dehydrogenase was allowed to act
upon a biological sample (e.g., plasma) in alkaline buffer in the
presence of nicotinamide adenine dinucleotide (NAD.sup.+), and an
amino group in a substrate contained in the biological sample was
oxidatively deaminated, as well as a reduced product (NADH) was
formed from nicotinamide adenine dinucleotide (NAD.sup.+). The
amount of NADH that formed was measured using a microplate reader
(SpectraMax M2e, supplied from Molecular Devices).
Example 1
Production of Modified Enzyme (I136R)
[0143] (1) Preparation of Template Ldh Gene
[0144] (a) Culture and Purification of Chromosomal DNA
[0145] A lyophilized pellet of Geobacillus stearothermophilus NBRC
12550 obtained from National Institute of Technology and
Evaluation, Biological Resource Center (NBRC) was suspended in a
growth medium 702, which was then applied onto an agar medium of a
growth medium 802 and cultured overnight at 50.degree. C. A
resulting colony was inoculated in 5 mL of the growth medium 702
and statically cultured at 50.degree. C. for 30 hours. Chromosomal
DNA was purified from 5 mL of this cell culture, and subjected to
the following experiment.
[0146] Details for preparing the media are as described in Table
3.
TABLE-US-00003 TABLE 3 Composition of media Growth medium 702
Polypeptone 10 g Yeast extract 2 g MgSO.sub.4.cndot.7H.sub.2O 1 g
Distilled water 1 L (pH 7.0) Growth medium 802 Polypeptone 10 g
Yeast extract 2 g MgSO.sub.4.cndot.7H.sub.2O 1 g Agar 15 g
Distilled water 1 L (pH 7.0)
[0147] (b) Preparation of Plasmid
[0148] pUC18His plasmid made by the method described in Biosci.
Biotechnol. Biochem. 2009; 73: 729-732 was purified from a culture
medium of recombinant Escherichia coli (E. coli JM109/pUC18His)
carrying a vector using Invisorb Spin Plasmid Mini Kit (supplied
from Invitek) according to manufacturer's protocol. Subsequently, 7
.mu.L of vector DNA of purified plasmid pUC18His, 2.5 .mu.L of
10.times.K buffer (supplied from Takara Bio Inc.) and each 0.8
.mu.L of PstI and BamHI were mixed, sterilized ultrapure water was
added to make a total volume of a reaction solution 25 .mu.L, and
then the mixture was treated with the restriction enzymes at
37.degree. C. for 3 hours. Then, 2 .mu.L of alkaline phosphatase
derived from shrimp (supplied from Roche) and 5 .mu.L of .times.10
alkaline phosphatase buffer were added to 25 .mu.L of the above
reaction solution, and sterilized ultrapure water was added to make
a total volume of a reaction solution 50 .mu.L, and then the
mixture was reacted at 37.degree. C. for one hour. The reaction
solution was purified by phenol/chloroform extraction and ethanol
precipitation to obtain 20 .mu.L of dephosphorylated pUC18His
vector DNA dissolved in a TE solution.
[0149] (c) Amplification of Leucine Dehydrogenase Gene
[0150] G. stearothermophilus chromosomal DNA was used as a
template, and a synthesized oligonucleotide primer 1:
5'-CCGGATCCGATGGAATTGTTCAAATATATGGAAAC-3' (SEQ ID NO:11) (supplied
from Hokkaido System Science Co., Ltd) containing a BamHI
recognition site sequence and a synthesized oligonucleotide primer
2: 5'-ACTGCAGTTATATTGCCGAAGCACC-3' (SEQ ID NO:12) (supplied from
Hokkaido System Science Co., Ltd) containing a PstI recognition
site sequence, which had been both made based on a leucine
dehydrogenase gene from G. stearothermophilus IFO 12550 (SEQ ID NO:
1; Biochemistry, 27, 9056 (1988)) were used in amplification of the
leucine dehydrogenase gene derived from G. stearothermophilus. As a
PCR reaction solution, 50 ng of chromosomal DNA, each 1 .mu.L of
the synthesized nucleotide primers at 100 pmol/.mu.L, 5 .mu.L of
ExTaq.times.10 buffer (supplied from Takara Bio Inc.), 5 .mu.L of
2.5 mM dNTP mixture (supplied from Takara Bio Inc.), and 1 .mu.L of
TaKaRa ExTaq DNA polymerase (supplied from Takara Bio Inc.) were
mixed, and sterilized ultrapure water was added to make a total
volume of the reaction solution 50 .mu.L. PCR was performed using
PTC-200 Peltier thermal cycler (supplied from MJ Research Japan),
and the reaction at 94.degree. C. for 30 seconds, 55.degree. C. for
30 seconds and 72.degree. C. for 2 minutes was repeated in 30
cycles.
[0151] A PCR product was electrophoresed, and two amplified
products (around 1400 bp and 1900 bp) cut out under ultraviolet
irradiation was extracted and purified using a gel extraction kit
Gel-M.TM. Gel Extraction Kit (supplied from VIOGENE) to obtain 50
.mu.L of a purified product. Subsequently, 6 .mu.L of 10.times.K
buffer (supplied from Takara Bio Inc.) and each 1 i.mu.L of PstI
and BamHI were added to 4 .mu.L of the purified product, and
sterilized ultrapure water was added to make a total volume of the
reaction solution 60 .mu.L. The reaction solution was reacted at
37.degree. C. for 3 hours to treat both ends of the purified PCR
product with the restriction enzymes. The reaction solution was
incubated at 60.degree. C. for 15 minutes to inactivate the
restriction enzymes. Subsequently the ethanol precipitation was
performed to obtain a purified insertion fragment.
[0152] (d) Ligation and Transformation
[0153] 1 .mu.L of the dephosphorylated plasmid obtained above, 5
.mu.L of the purified insertion fragment, and 6 .mu.L of Ligation
Mix (supplied from Takara Bio Inc.) were mixed, a total volume of a
reaction solution was made 12 .mu.L, and a ligation reaction was
performed at 16.degree. C. overnight. Subsequently, E. coli JM109
was transformed with 6 .mu.L of the reaction solution after the
ligation reaction, applied onto an LB agar medium containing 50
.mu.g/mL of ampicillin, and cultured at 37.degree. C. for 10 hours.
A resulting colony was inoculated to a master plate and cultured,
and then a newly formed colony was inoculated to 5 mL of the LB
agar medium containing 50 .mu.g/mL of ampicillin and cultured
overnight. Plasmid DNA was purified from the culture, and its
nucleotide sequence was analyzed using ABI PRISM 310 Genetic
Analyzer (supplied from Applied Biosystems). A clone confirmed to
have the correct nucleotide sequence of the leucine dehydrogenase
gene derived from G. stearothermophilus was designated as E. coli
JM109/pUCHisLDH.
[0154] (2) Production of Modified Enzyme of Leucine Dehydrogenase
Derived from Geobacillus stearothermophilus
[0155] An expression plasmid for a modified enzyme (I136R) was made
by introducing a site-directed mutation into pUCHisLDH using
QuikChange Lightning Site-Directed Mutagenesis Kits (Agilent
Technologies) according to the protocol attached to the product. At
that time, a sequence: 5'-GACTATGTCACCGGCCGTTCGCCCGAATTCGG-3' (SEQ
ID NO:9) and a sequence: 5'-CCGAATTCGGGCGAACGGCCGGTGACATAGTC-3'
(SEQ ID NO:10) were used as a sense primer containing a mutated
codon and an antisense primer, respectively. Experimental
manipulations associated with transformation, cultivation, plasmid
extraction, and the like were carried out according to standard
methods. A clone identified to have an objective nucleotide
sequence was designated as Escherichia coli JM109/pUCHisLDH mutant
and used for subsequent experiments.
[0156] (3) Expression and Purification of Modified Enzyme
[0157] Expression and purification of the modified enzyme
constructed as described previously are shown below. A colony of
recombinant Escherichia coli transformed with the plasmid pUCHisLDH
mutant containing the gene encoding the modified enzyme
(Escherichia coli JM109/pUCHisLDH mutant) was cultured with shaking
in a test tube containing 5 mL of the LB medium containing 50
.mu.g/mL of ampicillin salt at 37.degree. C. for 16 hours. This
culture was inoculated to a 0.5 liter Sakaguchi flask containing
100 mL of the LB medium containing 50 .mu.g/mL of ampicillin salt,
and cultured with shaking at 37.degree. C. until O.D. reached 1.0.
Then, 1 M isopropyl-.beta.-D-galactoside (IPTG supplied from
Nacalai Tesque Inc.) was added at a final concentration of 1 mM,
and the cultivation with shaking was further continued for
additional 5 hours. The resulting cultured medium was centrifuged
(8,000 rpm, 15 minutes, 4.degree. C.; Hitachi high speed cooled
centrifuge, HIMAC CR21G supplied from Hitachi Ltd.) to precipitate
cultured microbial cells, and a supernatant was discarded. The
obtained microbial cells were suspended in 50 mM NaH.sub.2PO.sub.4
buffer (pH 8.0) containing 300 mM NaCl and 10 mM imidazole. Then,
the microbial cells were disrupted and the enzyme was extracted
using an ultrasonic disruption apparatus (KUBOTA INSONATOR model
201M, supplied from Kubota Corporation) at 180 W for 15 minutes at
4.degree. C. A cell lysate was centrifuged (8,000 rpm, 15 minutes,
4.degree. C.; Hitachi high speed cooled centrifuge, HIMAC CR21G
supplied from Hitachi Ltd.) and a supernatant was used as a
cell-free extract solution for the purification of an enzymatic
protein. The cell-free extract solution was applied onto a column
filled with 1 mL of Ni-NTA resin (supplied from Qiagen) and
equilibrated with buffer (50 mM NaH.sub.2PO.sub.4 buffer (pH 8.0)
containing 300 mM NaCl and 10 mM imidazole). The resin was washed
with 5 mL of washing buffer (50 mM NaH.sub.2PO.sub.4 buffer (pH
6.5) containing 1 M NaCl and 20 mM imidazole), and subsequently a
bound enzymatic protein was eluted with 5 mL of elution buffer (50
mM NaH.sub.2PO.sub.4 buffer (pH 8.0) containing 300 mM NaCl and 250
mM imidazole). The eluted fraction was concentrated using an
ultrafiltration membrane (e.g., Vivaspin6 100 kDa MWCO supplied
from GE Healthcare). A protein concentration was measured using
Micro BCA Protein Assay Kit (supplied from Thermo Fisher
Scientific) and calculated based on a standard curve prepared using
predetermined concentration of bovine serum albumin. A purity of
the purified enzyme was confirmed by sodium dodecyl
sulfate/polyacrylamide gel electrophoresis. Subsequent experiments
were carried out using the obtained purified enzyme.
Example 2
Evaluation of Substrate Specificity
[0158] An activity of leucine dehydrogenase was measured in a
cuvette with 1 cm of an optical pass length (supplied from Bio-Rad)
using a microplate reader also capable of using a cuvette
(SpectraMax M2e, supplied from Molecular Devices) according to
Asano et al.'s method (Eur. J. Biochem. (1987) 168 (1), 153-159). A
composition of a reaction solution was as follows. 0.5 mL of 0.2 M
Glycine-KCl--KOH buffer (pH9.0), 0.04 mL of a solution of 25 mM
NAD.sup.+ (supplied from Sigma), and 0.1 mL of a solution of 0.1 M
L-leucine (supplied from Sigma) or L-isoleucine (supplied from
Sigma) or L-valine (supplied from Sigma) and an appropriate amount
of an enzyme solution were added to make a total volume of the
reaction solution 1.0 mL. An enzymatic reaction was performed at
room temperature for one minute, and change of an absorbance at 340
nm was measured. The results are shown in FIG. 2. A relative
activity of the modified enzyme (I136R) to which the mutation had
been introduced using the wild-type (WT) as the template was
improved for each BCAA. Hereinafter, the wild-type is sometimes
abbreviated as WT.
Example 3
Preparation of Standard Curve for Reaction of BCAA with Modified
Enzyme (I136R)
[0159] 0.5 mL of 0.2 M Glycine-KCl--KOH buffer (pH9.0), 0.04 mL of
a solution of 25 mM NAD.sup.+ (supplied from Sigma), and a known
concentration of an L-leucine or L-isoleucine or L-valine aqueous
solution were mixed, and MilliQ water was added to make a total
volume of 0.96 mL. This mixture was added to a cuvette. To this
solution, 0.04 mL of 0.5 mg/mL enzyme solution was added to make a
total volume of 1 mL, and the resulting solution was mixed upside
down. The enzymatic reaction was performed at room temperature for
one minute, and the change of the absorbance at 340 nm was
measured.
[0160] The results of the above measurement are shown in FIG. 3.
When BCAA concentrations were 140 to 560 .mu.M (measured at 4
points of 140, 280, 420 and 560 .mu.M), the standard curves for
Leu, Ile and Val were largely different in the case of WT because
the activity of WT for each BCAA was different. On the other hand,
the standard curves for the reaction of Leu, Ile and Val with the
modified enzyme I136R were almost the same because its activity for
each BCAA was almost the same. From the above, it was revealed that
according to the modified enzyme I136R, the total BCAA
concentration in even a sample containing any two or all of Leu,
Ile and Val in mixture could be considered as concentration of any
one of Leu, Ile and Val.
Example 4
Quantification of Total BCAA in Actual Sample by Modified Enzyme
I136R
[0161] Rat plasma samples (SD strain, females, 20 weeks of age,
supplied from Charles River Laboratories Japan, Inc.) were used as
actual samples, and total BCAA in the sample was measured by LeuDH
WT and LeuDH I136R. The measurement was evaluated by comparing
total BCAA measurement values calculated by the enzymatic method
with total BCAA measurement values obtained by an amino acid
analyzer L-8900 (supplied from Hitachi High Technologies
Corporation).
[0162] The quantification of total BCAA by the enzymatic method was
carried out according to the following procedure. 0.5 mL of 0.2 M
Glycine-KCl--KOH buffer (pH9.0), 0.04 mL of a solution of 25 mM
NAD.sup.+ (supplied from Sigma), and 0.04 mL or 0.02 mL of a known
concentration of an L-valine aqueous solution or a rat plasma
sample were mixed, and MilliQ water was added to make a total
volume of 0.96 mL. This mixture was added to a cuvette. To this
solution, 0.04 mL of 0.5 mg/mL enzyme solution was added to make a
total volume of 1 mL, and the resulting solution was mixed upside
down. The enzymatic reaction was performed at room temperature for
one minute, and the change of the absorbance at 340 nm was
measured. The total BCAA in the plasma sample was quantified using
a standard curve made by using the L-valine aqueous solution.
[0163] Deproteinization by sulfosalicylic acid was performed in the
rat plasma samples for measuring by the amino acid analyzer.
[0164] A graph comparing respective measurement values of the total
BCAA concentration in the rat plasma samples obtained by the
enzymatic method and by the amino acid analyzer is shown in FIG. 4.
As a result, the measurement values of the total BCAA concentration
in the actual samples obtained by the enzymatic method were almost
the same as the measurement values of the total BCAA obtained by
the amino acid analyzer. The wild-type leucine dehydrogenase is
known to scarcely have a catalytic activity for amino acids other
than the branched-chain amino acids. The BCAA in the plasma sample
containing a plurality of amino acids could be quantified in this
experiment. Thus, the modified enzyme of the present invention is
predicted to retain the property of the wild-type enzyme that the
wild-type enzyme scarcely has the catalytic activity for the amino
acids other than the branched chain amino acids. As described
above, it was demonstrated that the modified enzyme of the present
invention was useful for the measurement specific for the total
BCAA in the actual sample.
Example 5
Synthesis of Modified Enzyme Using Cell-Free System and
Purification of Modified Enzyme
[0165] A histidine affinity tag and a TEV protease recognition site
were fused to an N terminal side by a 2-step PCR method using a
wild-type gene or an objective mutant gene as a template to prepare
linear DNA of a construct having an introduced objective mutation.
A protein was synthesized in a cell-free synthesis reaction system
derived from Escherichia coli using this DNA as the template. A
supernatant fraction after centrifugation of a product synthesized
by a dialysis method for 6 hours using 1 mL of a reaction scale was
purified with affinity for Ni to yield an elution fraction.
Subsequently, the presence of a protein conceivable to be an
objective enzyme was identified by SDS-PAGE and staining using
SYPRO ORANGE protein gel stain (Life Technologies Japan Ltd.). A
protein concentration in the yielded elution fraction was
quantified by the Bradford method using BSA as a standard
substance. The elution fraction was adjusted to an objective
concentration as needed, and subsequently subjected to the
evaluation. For the wild-type enzyme, the preparation of linear
DNA, the cell-free synthesis, and the purification and analysis of
the enzyme were performed in the same manner as above. Enzymes
prepared by PCR using the wild-type gene as the template are shown
in Table 4. Enzymes prepared by PCR using the gene carrying the
introduced objective mutation as the template are shown in Tables 5
and 6. The resin and the buffer used for the purification are as
follows.
[0166] Resin: Ni Sepharose High Performance (GE Healthcare
Japan)
[0167] Buffer: Binding Buffer (NaCl 750 mM, NaPi 20 mM, pH8.0),
[0168] Wash Buffer (NaCl 750 mM, NaPi 20 mM, pH8.0)
[0169] Collection and measurement Buffer (NaCl 300 mM, NaPi 50 mM,
EDTA 34 mM, pH7.0, 10% D.sub.2O, 0.01% NaN.sub.3)
Example 6
Evaluation of Activity and Substrate Specificity
[0170] The activity and the relative activity of the wild-type
enzyme and the modified enzyme synthesized in Example 5 were
evaluated according to the method in Example 2. The results are
shown in Tables 4, 5 and 6. Mean values of results from 3 samples
of the wild-type were used for values from WT in Tables 4 and 5.
The results in Table 6 were calculated from mean values when the
experiment was performed three times for the same sample. When the
modified enzyme having a plurality of introduced mutations is
represented, each of the introduced mutations was marked off using
a slash and described consecutively. For example, a mutant
I136R/I292F denotes a modified enzyme having two mutations of I136R
and I292F. By introducing the mutation, the activity of the
modified enzyme was further enhanced and/or became more equivalent
for each BCAA, compared to that of WT. Compared to the case of
introducing one mutation, the relative value of the activity for
each BCAA became more equivalent by introducing two mutations that
made the relative value more equivalent than WT.
TABLE-US-00004 TABLE 4 Relative values of activity of modified
enzymes relative to WT (left) and relative values of activity of
enzymes for each BCAA (right) (1). Activity (change of Relative
activity (when activity absorbance per one minute) for Leu is
regarded as 100%) Leu Ile Val Leu Ile Val I136C 258% 242% 318%
I136C 100% 80% 86% I136Y 204% 218% 241% I136Y 100% 91% 83% I136A
188% 183% 221% I136A 100% 82% 82% I136G 162% 157% 220% I136G 100%
82% 95% I136S 148% 150% 172% I136S 100% 86% 81% I136N 142% 137%
153% I136N 100% 82% 76% I136W 137% 152% 152% I136W 100% 94% 78%
I136Q 108% 113% 113% I136Q 100% 88% 73% I136E 97% 82% 92% I136E
100% 71% 66% I136T 95% 95% 93% I136T 100% 85% 69% I136P 92% 70% 96%
I136P 100% 65% 73% I136D 55% 50% 55% I136D 100% 76% 69% I292H 245%
270% 307% I292H 100% 93% 88% I292N 241% 274% 304% I292N 100% 96%
88% I292Y 234% 265% 274% I292Y 100% 96% 82% I292L 231% 218% 244%
I292L 100% 80% 74% I292K 231% 248% 264% I292K 100% 91% 80% I292Q
223% 250% 262% I292Q 100% 95% 82% I292R 211% 213% 229% I292R 100%
86% 76% I292D 208% 186% 242% I292D 100% 76% 81% I292T 202% 218%
226% I292T 100% 91% 78% I292E 200% 195% 233% I292E 100% 83% 82%
I292S 195% 213% 219% I292S 100% 93% 78% I292C 161% 165% 154% I292C
100% 87% 67% I292A 157% 170% 175% I292A 100% 92% 78% I292G 145%
158% 171% I292G 100% 92% 82% I292V 128% 134% 133% I292V 100% 89%
73% I292W 120% 138% 117% I292W 100% 97% 68% I292P 73% 63% 75% I292P
100% 73% 72% WT 100% 100% 100% WT 100% 85% 70%
TABLE-US-00005 TABLE 5 Relative values of activity of modified
enzymes relative to WT (left) and relative values of activity of
enzymes for each BCAA (right) (2). Activity (change of Relative
activity (when activity absorbance per one minute) for Leu is
regarded as 100%) Leu Ile Val Leu Ile Val I136M 250% 300% 370%
I136M 100% 93% 102% I136R 239% 279% 330% I136R 100% 91% 95% I136H
191% 206% 180% I136H 100% 83% 65% I136F 184% 238% 277% I136F 100%
100% 102% I136L 180% 171% 240% I136L 100% 73% 92% I136K 150% 171%
217% I136K 100% 88% 99% I136V 75% 65% 63% I136V 100% 66% 57% I292F
268% 362% 370% I292F 100% 105% 95% WT 100% 100% 100% WT 100% 76%
66%
TABLE-US-00006 TABLE 6 Relative values of activity of modified
enzymes relative to WT (left) and relative values of activity of
enzymes for each BCAA (right) (3). Relative activity Activity
(change of (when activity for Leu absorbance per one minute) is
regarded as 100%) Leu Ile Val Leu Ile Val I136R/I292F 158% 214%
232% I136R/I292F 100% 101% 94% WT 100% 100% 100% WT 100% 75%
64%
[0171] A 96-well microwell plate was used in place of the cuvette
having 1 cm of the optical pass length, an enzymatic reaction was
performed in the following reaction solution at 30.degree. C. for
one minutes, and then the change of the absorbance at 340 nm was
measured. An enzyme to be used was synthesized using the linear DNA
prepared using the wild-type gene as the template and purified as
shown in Example 5. The reaction solution was prepared by mixing
150 .mu.L of buffer (0.2 M HEPES, 0.28 M sodium chloride, 8.4 mM
disodium hydrogen phosphate, pH 7.0 or 7.5 or 8.0), 30 .mu.L of an
aqueous solution of 25 mM NAD.sup.+, 1.5 .mu.L of an aqueous
solution of 1 M potassium chloride, 3 .mu.L of an aqueous solution
of 10 mM L-leucine or L-isoleucine or L-valine and 100.5 .mu.L of
MilliQ water, and further adding 15 .mu.L of 1 mg/mL of an enzyme
solution thereto. The results are shown in Tables 7 and 8. Each
value for I136K and I136R was obtained from one experiment, and
other values for other enzymes were mean values calculated from two
experiments for the same sample. Table 7 shows relative values of
the activity of the modified enzymes relative to WT, and Table 8
shows relative values of activity of the enzymes for each BCAA.
TABLE-US-00007 TABLE 7 Relative values of activity of modified
enzymes relative to WT. Activity (change of absorbance per one
minute) pH 7.0 pH 7.5 pH 8.0 Leu Ile Val Leu Ile Val Leu Ile Val
I136A 258% 182% 412% 174% 164% 234% 143% 176% 210% I136C 328% 233%
610% 206% 206% 314% 157% 218% 285% I136E 69% 47% 66% 40% 35% 30%
27% 25% 17% I136F 252% 270% 538% 152% 208% 255% 136% 194% 214%
I136G 270% 207% 488% 188% 188% 255% 153% 201% 219% I136H 292% 251%
375% 191% 223% 211% 157% 199% 186% I136K 231% 219% 436% 170% 200%
236% 152% 188% 203% I136L 291% 236% 497% 185% 219% 271% 158% 196%
227% I136M 317% 265% 588% 179% 240% 327% 153% 226% 277% I136N 235%
199% 301% 187% 171% 176% 150% 167% 139% I136Q 84% 112% 175% 89% 96%
75% 81% 99% 68% I136R 283% 271% 579% 167% 235% 294% 145% 217% 245%
I136S 166% 165% 274% 148% 151% 143% 130% 154% 123% I136T 64% 68%
77% 71% 65% 57% 69% 70% 56% I136V 76% 69% 99% 73% 66% 64% 81% 75%
68% I136W 195% 169% 221% 146% 146% 134% 119% 133% 110% I136Y 257%
236% 522% 168% 193% 244% 134% 178% 201% I292A 208% 176% 309% 160%
185% 180% 132% 162% 178% I292C 224% 185% 335% 177% 184% 199% 146%
168% 164% I292D 396% 339% 739% 236% 278% 359% 183% 253% 277% I292E
335% 381% 666% 216% 325% 359% 162% 267% 287% I292F 396% 532% 817%
231% 397% 367% 180% 327% 281% I292G 324% 296% 561% 210% 261% 296%
165% 225% 243% I292H 357% 408% 756% 200% 326% 350% 158% 294% 269%
I292K 372% 342% 588% 211% 296% 300% 168% 249% 255% I292L 365% 380%
544% 210% 302% 282% 158% 250% 242% I292M 245% 192% 361% 180% 179%
206% 157% 183% 195% I292N 332% 463% 784% 188% 375% 364% 147% 310%
294% I292Q 352% 434% 706% 207% 377% 346% 153% 287% 272% I292R 380%
329% 653% 213% 316% 325% 171% 284% 257% I292S 353% 363% 640% 211%
311% 326% 163% 265% 270% I292T 305% 313% 495% 200% 267% 294% 153%
225% 244% I292V 136% 102% 144% 103% 105% 106% 99% 104% 106% I292W
165% 231% 194% 125% 189% 123% 116% 154% 110% I292Y 352% 481% 753%
205% 358% 316% 159% 268% 231% I136F/I292F 143% 363% 517% 104% 218%
221% 89% 158% 161% I136R/I292F 235% 428% 591% 141% 285% 242% 115%
185% 178% WT 100% 100% 100% 100% 100% 100% 100% 100% 100%
TABLE-US-00008 TABLE 8 Relative values of activity of enzymes for
each BCAA. Relative activity (when activity for Leu is regarded as
100%) pH 7.0 pH 7.5 pH 8.0 Leu Ile Val Leu Ile Val Leu Ile Val
I136A 100% 57% 97% 100% 70% 106% 100% 95% 115% I136C 100% 57% 113%
100% 75% 120% 100% 107% 141% I136E 100% 55% 58% 100% 65% 59% 100%
72% 48% I136F 100% 86% 129% 100% 102% 133% 100% 111% 123% I136G
100% 62% 110% 100% 75% 107% 100% 102% 112% I136H 100% 69% 78% 100%
87% 87% 100% 98% 92% I136K 100% 76% 115% 100% 88% 109% 100% 96%
104% I136L 100% 65% 104% 100% 88% 116% 100% 96% 112% I136M 100% 67%
113% 100% 100% 144% 100% 114% 142% I136N 100% 68% 78% 100% 68% 74%
100% 86% 72% I136Q 100% 107% 126% 100% 81% 67% 100% 95% 66% I136R
100% 77% 124% 100% 105% 139% 100% 115% 132% I136S 100% 80% 100%
100% 76% 76% 100% 92% 74% I136T 100% 85% 73% 100% 69% 63% 100% 78%
63% I136V 100% 72% 78% 100% 68% 70% 100% 72% 65% I136W 100% 69% 69%
100% 74% 72% 100% 86% 73% I136Y 100% 74% 123% 100% 86% 115% 100%
103% 118% I292A 100% 68% 90% 100% 86% 89% 100% 95% 105% I292C 100%
67% 91% 100% 78% 89% 100% 89% 88% I292D 100% 69% 113% 100% 88% 120%
100% 107% 118% I292E 100% 92% 121% 100% 112% 131% 100% 127% 138%
I292F 100% 108% 125% 100% 128% 125% 100% 141% 122% I292G 100% 73%
105% 100% 93% 111% 100% 105% 115% I292H 100% 92% 128% 100% 122%
139% 100% 144% 133% I292K 100% 74% 96% 100% 105% 112% 100% 115%
119% I292L 100% 84% 90% 100% 107% 106% 100% 122% 119% I292M 100%
63% 89% 100% 74% 90% 100% 90% 97% I292N 100% 112% 143% 100% 149%
153% 100% 164% 157% I292Q 100% 99% 122% 100% 136% 132% 100% 145%
139% I292R 100% 70% 104% 100% 110% 120% 100% 129% 118% I292S 100%
83% 110% 100% 110% 122% 100% 126% 130% I292T 100% 82% 98% 100% 100%
116% 100% 113% 124% I292V 100% 60% 64% 100% 76% 81% 100% 81% 84%
I292W 100% 113% 71% 100% 112% 77% 100% 103% 74% I292Y 100% 110%
130% 100% 131% 122% 100% 131% 114% I136F/I292F 100% 203% 219% 100%
155% 168% 100% 137% 141% I136R/I292F 100% 147% 153% 100% 151% 136%
100% 125% 122% WT 100% 80% 61% 100% 75% 79% 100% 77% 78%
Example 7
Evaluation of Thermal Stability
[0172] Five solutions of LeuDH WT and the following modified
enzymes synthesized in Example 5 were treated with heat at 60, 70
and 80.degree. C. for one hour, and subsequently the activity was
measured. A remaining activity of each enzyme solution after the
treatment with heat is shown in Table 9. The remaining activity of
any modified enzyme after the treatment with heat at 60.degree. C.
or 70.degree. C. was higher than that of WT.
TABLE-US-00009 TABLE 9 Relative activity after treatment with heat
at indicated reaction temperature when activity before treatment is
regarded as 100. WT I292F I136K I136F I136R I136M 60.degree. C. 74
92 86 90 91 96 70.degree. C. 58 62 67 74 75 74 80.degree. C. 0 0 0
0 0 1
INDUSTRIAL APPLICABILITY
[0173] The modified enzyme of the present invention is useful for
the rapid measurement of the total branched-chain amino acid
concentration. The modified enzyme of the present invention is also
useful for the measurement of any branched-chain amino acid and/or
the production of derivatives of any branched-chain amino acid. The
modified enzyme of the present invention is further useful as a
liquid reagent. The analysis method of the present invention is
useful for the diagnosis of diseases such as cirrhosis or hepatic
encephalopathy.
[0174] While the invention has been described in detail with
reference to preferred embodiments thereof, it will be apparent to
one skilled in the art that various changes can be made, and
equivalents employed, without departing from the scope of the
invention. Each of the aforementioned documents is incorporated by
reference herein in its entirety.
Sequence CWU 1
1
1011104DNAGeobacillus stearothermophilus 1atggaattgt tcaaatatat
ggaaacttac gattatgagc aagtgctgtt ttgccaagat 60aaagaatcgg gtttgaaagc
gatcattgcc attcatgaca caacgctcgg cccggcgctc 120ggcgggacgc
gcatgtggat gtacaattcg gaagaagaag cgcttgaaga cgccttgcgc
180ctcgcccgcg gcatgacgta caaaaacgcg gccgccggcc tcaacttggg
cgggggcaaa 240acggtcatca tcggcgaccc gcgcaaagat aaaaacgaag
cgatgttccg ggcgttcggc 300cgcttcattc aagggctgaa cggccgctac
atcacggcgg aagacgtcgg cacgaccgtc 360gccgatatgg atatcatcta
tcaagaaacc gactatgtca ccggcatttc gcccgaattc 420ggctcatccg
gcaacccatc gccggcgacc gcctacggcg tataccgcgg catgaaggcg
480gcggcaaaag aggcgttcgg cagcgattcg ctcgaaggaa aagtcgtcgc
cgtccaagga 540gtcggcaatg tcgcgtatca tttgtgccgc catttgcacg
aagaaggagc gaaactcatc 600gtgactgaca tcaacaagga agtggtggcg
cgcgcggtcg aggaattcgg agcgaaagcg 660gtcgacccga acgacattta
cggcgtggag tgcgacattt ttgctccatg cgcgctcggc 720ggcatcatca
acgatcaaac gattccgcaa ctgaaagcga aagtgatcgc cggatcggca
780gacaaccagc tgaaagagcc gcgccatggc gacatcatcc atgaaatggg
catcgtctat 840gccccggatt atgtgatcaa cgccggcggc gtcatcaacg
tcgcggacga actgtacggc 900tacaatcggg aacgggcgat gaaaaaaatc
gagcaaattt atgacaacat cgaaaaagtg 960tttgccatcg ccaagcgcga
caacattcca acgtatgtgg ccgccgaccg gatggcggaa 1020gaacggattg
aaacgatgcg caaagcgcgc agtccatttt tgcaaaatgg tcaccatatt
1080ttaagccgcc gtcgcgcccg ctaa 11042367PRTGeobacillus
stearothermophilus 2Met Glu Leu Phe Lys Tyr Met Glu Thr Tyr Asp Tyr
Glu Gln Val Leu 1 5 10 15 Phe Cys Gln Asp Lys Glu Ser Gly Leu Lys
Ala Ile Ile Ala Ile His 20 25 30 Asp Thr Thr Leu Gly Pro Ala Leu
Gly Gly Thr Arg Met Trp Met Tyr 35 40 45 Asn Ser Glu Glu Glu Ala
Leu Glu Asp Ala Leu Arg Leu Ala Arg Gly 50 55 60 Met Thr Tyr Lys
Asn Ala Ala Ala Gly Leu Asn Leu Gly Gly Gly Lys 65 70 75 80 Thr Val
Ile Ile Gly Asp Pro Arg Lys Asp Lys Asn Glu Ala Met Phe 85 90 95
Arg Ala Phe Gly Arg Phe Ile Gln Gly Leu Asn Gly Arg Tyr Ile Thr 100
105 110 Ala Glu Asp Val Gly Thr Thr Val Ala Asp Met Asp Ile Ile Tyr
Gln 115 120 125 Glu Thr Asp Tyr Val Thr Gly Ile Ser Pro Glu Phe Gly
Ser Ser Gly 130 135 140 Asn Pro Ser Pro Ala Thr Ala Tyr Gly Val Tyr
Arg Gly Met Lys Ala 145 150 155 160 Ala Ala Lys Glu Ala Phe Gly Ser
Asp Ser Leu Glu Gly Lys Val Val 165 170 175 Ala Val Gln Gly Val Gly
Asn Val Ala Tyr His Leu Cys Arg His Leu 180 185 190 His Glu Glu Gly
Ala Lys Leu Ile Val Thr Asp Ile Asn Lys Glu Val 195 200 205 Val Ala
Arg Ala Val Glu Glu Phe Gly Ala Lys Ala Val Asp Pro Asn 210 215 220
Asp Ile Tyr Gly Val Glu Cys Asp Ile Phe Ala Pro Cys Ala Leu Gly 225
230 235 240 Gly Ile Ile Asn Asp Gln Thr Ile Pro Gln Leu Lys Ala Lys
Val Ile 245 250 255 Ala Gly Ser Ala Asp Asn Gln Leu Lys Glu Pro Arg
His Gly Asp Ile 260 265 270 Ile His Glu Met Gly Ile Val Tyr Ala Pro
Asp Tyr Val Ile Asn Ala 275 280 285 Gly Gly Val Ile Asn Val Ala Asp
Glu Leu Tyr Gly Tyr Asn Arg Glu 290 295 300 Arg Ala Met Lys Lys Ile
Glu Gln Ile Tyr Asp Asn Ile Glu Lys Val 305 310 315 320 Phe Ala Ile
Ala Lys Arg Asp Asn Ile Pro Thr Tyr Val Ala Ala Asp 325 330 335 Arg
Met Ala Glu Glu Arg Ile Glu Thr Met Arg Lys Ala Arg Ser Pro 340 345
350 Phe Leu Gln Asn Gly His His Ile Leu Ser Arg Arg Arg Ala Arg 355
360 365 31095DNALysinibacillus sphaericus 3atggaaatct tcaagtatat
ggaaaagtat gattatgaac aattggtatt ttgccaagac 60gaagcatctg ggttaaaagc
gattatcgct atccatgaca caacacttgg accagcatta 120ggtggtgctc
gtatgtggac ctacgcgaca gaagaaaatg cgattgagga tgcattaaga
180ttagcacgcg ggatgacata taaaaatgca gctgctggtt taaaccttgg
cggtggaaaa 240acggtcatta ttggggaccc atttaaagat aaaaacgaag
aaatgttccg tgctttaggt 300cgtttcattc aaggattaaa cggtcgctat
attaccgctg aagatgttgg tacaaccgta 360acagatatgg atttaatcca
tgaggaaaca aattacgtta caggtatatc gccagcgttt 420ggttcatcgg
gtaatccttc accagtaact gcttatggcg tttatcgtgg catgaaagca
480gcggcgaaag aagcatttgg tacggatatg ctagaaggtc gtactatatc
ggtacaaggg 540ctaggaaacg tagcttacaa gctttgcgag tatttacata
atgaaggtgc aaaacttgta 600gtaacagata ttaaccaagc ggctattgat
cgtgttgtca atgattttgg cgctacagca 660gttgcacctg atgaaatcta
ttcacaagaa gtcgatattt tctcaccgtg tgcacttggc 720gcaattttaa
atgacgaaac gattccgcaa ttaaaagcaa aagttattgc tggttctgct
780aataaccaac tacaagattc acgacatgga gattatttac acgagctagg
cattgtttat 840gcacctgact atgtcattaa tgcaggtggt gtaataaatg
tcgcggacga attatatggc 900tataatcgtg aacgagcgtt gaaacgtgta
gatggtattt acgatagtat tgaaaaaatc 960tttgaaattt ccaaacgtga
tagtattcca acatatgttg cggcaaatcg tttggcagaa 1020gaacgtattg
ctcgtgtagc gaaatcgcgt agtcagttct taaaaaatga aaaaaatatt
1080ttgaacggcc gttaa 10954364PRTLysinibacillus sphaericus 4Met Glu
Ile Phe Lys Tyr Met Glu Lys Tyr Asp Tyr Glu Gln Leu Val 1 5 10 15
Phe Cys Gln Asp Glu Ala Ser Gly Leu Lys Ala Ile Ile Ala Ile His 20
25 30 Asp Thr Thr Leu Gly Pro Ala Leu Gly Gly Ala Arg Met Trp Thr
Tyr 35 40 45 Ala Thr Glu Glu Asn Ala Ile Glu Asp Ala Leu Arg Leu
Ala Arg Gly 50 55 60 Met Thr Tyr Lys Asn Ala Ala Ala Gly Leu Asn
Leu Gly Gly Gly Lys 65 70 75 80 Thr Val Ile Ile Gly Asp Pro Phe Lys
Asp Lys Asn Glu Glu Met Phe 85 90 95 Arg Ala Leu Gly Arg Phe Ile
Gln Gly Leu Asn Gly Arg Tyr Ile Thr 100 105 110 Ala Glu Asp Val Gly
Thr Thr Val Thr Asp Met Asp Leu Ile His Glu 115 120 125 Glu Thr Asn
Tyr Val Thr Gly Ile Ser Pro Ala Phe Gly Ser Ser Gly 130 135 140 Asn
Pro Ser Pro Val Thr Ala Tyr Gly Val Tyr Arg Gly Met Lys Ala 145 150
155 160 Ala Ala Lys Glu Ala Phe Gly Thr Asp Met Leu Glu Gly Arg Thr
Ile 165 170 175 Ser Val Gln Gly Leu Gly Asn Val Ala Tyr Lys Leu Cys
Glu Tyr Leu 180 185 190 His Asn Glu Gly Ala Lys Leu Val Val Thr Asp
Ile Asn Gln Ala Ala 195 200 205 Ile Asp Arg Val Val Asn Asp Phe Gly
Ala Thr Ala Val Ala Pro Asp 210 215 220 Glu Ile Tyr Ser Gln Glu Val
Asp Ile Phe Ser Pro Cys Ala Leu Gly 225 230 235 240 Ala Ile Leu Asn
Asp Glu Thr Ile Pro Gln Leu Lys Ala Lys Val Ile 245 250 255 Ala Gly
Ser Ala Asn Asn Gln Leu Gln Asp Ser Arg His Gly Asp Tyr 260 265 270
Leu His Glu Leu Gly Ile Val Tyr Ala Pro Asp Tyr Val Ile Asn Ala 275
280 285 Gly Gly Val Ile Asn Val Ala Asp Glu Leu Tyr Gly Tyr Asn Arg
Glu 290 295 300 Arg Ala Leu Lys Arg Val Asp Gly Ile Tyr Asp Ser Ile
Glu Lys Ile 305 310 315 320 Phe Glu Ile Ser Lys Arg Asp Ser Ile Pro
Thr Tyr Val Ala Ala Asn 325 330 335 Arg Leu Ala Glu Glu Arg Ile Ala
Arg Val Ala Lys Ser Arg Ser Gln 340 345 350 Phe Leu Lys Asn Glu Lys
Asn Ile Leu Asn Gly Arg 355 360 51101DNABacillus cereus 5atgacattag
aaatcttcga atacttagaa aaatatgatt atgagcaagt agtattttgt 60caagataaag
aatctggttt aaaagcaatt attgcaattc atgatacaac acttggaccg
120gctcttggtg gaacaagaat gtggacatat gattctgaag aagcggcgat
tgaagatgca 180ttgcgtcttg caaaagggat gacatacaaa aacgcagcag
ctggtttaaa cttaggtggt 240gcgaaaacag taattatcgg tgatcctcgt
aaagataaga gcgaagcaat gttccgtgca 300ctaggacgtt atatccaagg
actaaacgga cgttacatta cagctgaaga tgttggtaca 360acagtagatg
atatggatat tatccatgaa gaaactgact ttgtaacagg tatctcacca
420tcattcggtt cttctggtaa cccatctccg gtaactgcat acggtgttta
ccgtggtatg 480aaagcagctg caaaagaagc tttcggtact gacaatttag
aaggaaaagt aattgctgtt 540caaggcgttg gtaacgtagc atatcaccta
tgcaaacatt tacacgctga aggagcaaaa 600ttaattgtta cagatattaa
taaagaagct gtacaacgtg ctgtagaaga attcggtgca 660tcagcagttg
aaccaaatga aatttacggt gttgaatgcg atatttacgc accatgtgca
720ctaggcgcaa cagttaatga tgaaactatt ccacaactta aagcaaaagt
aatcgcaggt 780tctgcgaata accaattaaa agaagatcgt catggtgaca
tcattcatga aatgggtatt 840gtatacgcac cagattatgt aattaatgca
ggtggcgtaa ttaacgtagc agacgaatta 900tatggataca atagagaacg
tgcactaaaa cgtgttgagt ctatttatga cacgattgca 960aaagtaatcg
aaatttcaaa acgcgatggc atagcaactt atgtagcggc agatcgtcta
1020gctgaagagc gcattgcaag cttgaagaat tctcgtagca cttacttacg
caacggtcac 1080gatattatta gccgtcgcta a 11016366PRTBacillus cereus
6Met Thr Leu Glu Ile Phe Glu Tyr Leu Glu Lys Tyr Asp Tyr Glu Gln 1
5 10 15 Val Val Phe Cys Gln Asp Lys Glu Ser Gly Leu Lys Ala Ile Ile
Ala 20 25 30 Ile His Asp Thr Thr Leu Gly Pro Ala Leu Gly Gly Thr
Arg Met Trp 35 40 45 Thr Tyr Asp Ser Glu Glu Ala Ala Ile Glu Asp
Ala Leu Arg Leu Ala 50 55 60 Lys Gly Met Thr Tyr Lys Asn Ala Ala
Ala Gly Leu Asn Leu Gly Gly 65 70 75 80 Ala Lys Thr Val Ile Ile Gly
Asp Pro Arg Lys Asp Lys Ser Glu Ala 85 90 95 Met Phe Arg Ala Leu
Gly Arg Tyr Ile Gln Gly Leu Asn Gly Arg Tyr 100 105 110 Ile Thr Ala
Glu Asp Val Gly Thr Thr Val Asp Asp Met Asp Ile Ile 115 120 125 His
Glu Glu Thr Asp Phe Val Thr Gly Ile Ser Pro Ser Phe Gly Ser 130 135
140 Ser Gly Asn Pro Ser Pro Val Thr Ala Tyr Gly Val Tyr Arg Gly Met
145 150 155 160 Lys Ala Ala Ala Lys Glu Ala Phe Gly Thr Asp Asn Leu
Glu Gly Lys 165 170 175 Val Ile Ala Val Gln Gly Val Gly Asn Val Ala
Tyr His Leu Cys Lys 180 185 190 His Leu His Ala Glu Gly Ala Lys Leu
Ile Val Thr Asp Ile Asn Lys 195 200 205 Glu Ala Val Gln Arg Ala Val
Glu Glu Phe Gly Ala Ser Ala Val Glu 210 215 220 Pro Asn Glu Ile Tyr
Gly Val Glu Cys Asp Ile Tyr Ala Pro Cys Ala 225 230 235 240 Leu Gly
Ala Thr Val Asn Asp Glu Thr Ile Pro Gln Leu Lys Ala Lys 245 250 255
Val Ile Ala Gly Ser Ala Asn Asn Gln Leu Lys Glu Asp Arg His Gly 260
265 270 Asp Ile Ile His Glu Met Gly Ile Val Tyr Ala Pro Asp Tyr Val
Ile 275 280 285 Asn Ala Gly Gly Val Ile Asn Val Ala Asp Glu Leu Tyr
Gly Tyr Asn 290 295 300 Arg Glu Arg Ala Leu Lys Arg Val Glu Ser Ile
Tyr Asp Thr Ile Ala 305 310 315 320 Lys Val Ile Glu Ile Ser Lys Arg
Asp Gly Ile Ala Thr Tyr Val Ala 325 330 335 Ala Asp Arg Leu Ala Glu
Glu Arg Ile Ala Ser Leu Lys Asn Ser Arg 340 345 350 Ser Thr Tyr Leu
Arg Asn Gly His Asp Ile Ile Ser Arg Arg 355 360 365
71095DNABacillus licheniformis 7atggaactat ttcgatatat ggaacagtat
gactacgagc aattggtatt ttgccaagat 60aaacagtccg gtttaaaagc gatcatcgcg
attcatgata cgacgctcgg gccggctctc 120ggcggcacaa gaatgtggac
atacgaaagt gaagaagccg caattgaaga tgcgctgcgc 180cttgcgcggg
gaatgaccta caaaaatgcg gcggccggac tgaacctcgg aggaggcaaa
240accgttatta tcggagatcc gcgcaaagat aaaaacgaag aaatgttccg
cgctttcggc 300cgctacattc aaggcttgaa cggcagatac atcacagccg
aagacgtcgg tacaaccgtt 360gaagatatgg acatcattca tgacgaaacc
gatttcgtta caggcatttc acctgctttc 420ggttcatcag gaaatccttc
tccggtaaca gcttacgggg tatataaagg gatgaaggcg 480gcggcgaaag
cggcattcgg aacggattcg cttgaaggca aaaccgttgc ggttcaaggc
540gtcggaaacg tggcctacaa cctgtgccgg cacctccacg aagaaggcgc
gaaactgatc 600gtgaccgaca tcaacaaaga agcagttgaa cgtgcagtcg
ccgaattcgg cgcccgcgcc 660gtcgatccgg atgatattta ttcgcaggaa
tgcgatatat atgcgccgtg tgccctcgga 720gcgacaatca acgatgatac
gattccgcag ctgaaagcca aagtgattgc cggggcagcc 780aacaaccagc
tgaaagaaac ccgccacggt gatcaaatcc acgacatggg catcgtttat
840gccccggact atgtcatcaa tgccggcggc gtcatcaatg tcgctgacga
gctttacggc 900tataattcgg agcgcgcgct gaagaaagtc gaaggcatct
acggaaacat tgaacgcgtc 960cttgaaattt cgaagcgcga ccgcattccg
acatacttgg ccgcagaccg tctggcggaa 1020gaacgaattg agcgcatgcg
ccaatcgaga agccaatttt tgcaaaacgg ccatcacatt 1080ttaagcagac gttaa
10958364PRTBacillus licheniformis 8Met Glu Leu Phe Arg Tyr Met Glu
Gln Tyr Asp Tyr Glu Gln Leu Val 1 5 10 15 Phe Cys Gln Asp Lys Gln
Ser Gly Leu Lys Ala Ile Ile Ala Ile His 20 25 30 Asp Thr Thr Leu
Gly Pro Ala Leu Gly Gly Thr Arg Met Trp Thr Tyr 35 40 45 Glu Ser
Glu Glu Ala Ala Ile Glu Asp Ala Leu Arg Leu Ala Arg Gly 50 55 60
Met Thr Tyr Lys Asn Ala Ala Ala Gly Leu Asn Leu Gly Gly Gly Lys 65
70 75 80 Thr Val Ile Ile Gly Asp Pro Arg Lys Asp Lys Asn Glu Glu
Met Phe 85 90 95 Arg Ala Phe Gly Arg Tyr Ile Gln Gly Leu Asn Gly
Arg Tyr Ile Thr 100 105 110 Ala Glu Asp Val Gly Thr Thr Val Glu Asp
Met Asp Ile Ile His Asp 115 120 125 Glu Thr Asp Phe Val Thr Gly Ile
Ser Pro Ala Phe Gly Ser Ser Gly 130 135 140 Asn Pro Ser Pro Val Thr
Ala Tyr Gly Val Tyr Lys Gly Met Lys Ala 145 150 155 160 Ala Ala Lys
Ala Ala Phe Gly Thr Asp Ser Leu Glu Gly Lys Thr Val 165 170 175 Ala
Val Gln Gly Val Gly Asn Val Ala Tyr Asn Leu Cys Arg His Leu 180 185
190 His Glu Glu Gly Ala Lys Leu Ile Val Thr Asp Ile Asn Lys Glu Ala
195 200 205 Val Glu Arg Ala Val Ala Glu Phe Gly Ala Arg Ala Val Asp
Pro Asp 210 215 220 Asp Ile Tyr Ser Gln Glu Cys Asp Ile Tyr Ala Pro
Cys Ala Leu Gly 225 230 235 240 Ala Thr Ile Asn Asp Asp Thr Ile Pro
Gln Leu Lys Ala Lys Val Ile 245 250 255 Ala Gly Ala Ala Asn Asn Gln
Leu Lys Glu Thr Arg His Gly Asp Gln 260 265 270 Ile His Asp Met Gly
Ile Val Tyr Ala Pro Asp Tyr Val Ile Asn Ala 275 280 285 Gly Gly Val
Ile Asn Val Ala Asp Glu Leu Tyr Gly Tyr Asn Ser Glu 290 295 300 Arg
Ala Leu Lys Lys Val Glu Gly Ile Tyr Gly Asn Ile Glu Arg Val 305 310
315 320 Leu Glu Ile Ser Lys Arg Asp Arg Ile Pro Thr Tyr Leu Ala Ala
Asp 325 330 335 Arg Leu Ala Glu Glu Arg Ile Glu Arg Met Arg Gln Ser
Arg Ser Gln 340 345 350 Phe Leu Gln Asn Gly His His Ile Leu Ser Arg
Arg 355 360 932DNAArtificial SequenceSense primer for preparing a
mutated leucine dehydrogenase 9gactatgtca ccggccgttc gcccgaattc gg
321032DNAArtificial SequenceAntisense primer for preparing a
mutated leucine dehydrogenase 10ccgaattcgg gcgaacggcc ggtgacatag tc
32
* * * * *
References