D-serine dehydratase and use thereof

Abstract

A novel D-serine quantification method that can overcome various disadvantages of a conventional D-serine quantification method; a novel enzyme that can be used in the D-serine quantification method; a gene encoding the enzyme; and the like. Specifically, a novel D-serine dehydratase including (a) a protein having an amino acid sequence set forth in SEQ ID NO: 1 or (b) a protein having an amino acid sequence homologous to the amino acid sequence set forth in SEQ ID NO: 1 and having a D-serine dehydratase activity; and a D-serine quantification method including the steps of reacting a sample with the enzyme, quantifying ammonia or pyruvic acid produced by the reaction, and calculating the amount of D-serine in the sample based on a value produced by the quantification.

1 . D-serine dehydratase comprising the following protein (a) or (b):
 (a) a protein having an amino acid sequence set forth in SEQ ID NO: 1; or   (b) a protein having an amino acid sequence homologous to the amino acid sequence set forth in SEQ ID NO: 1 and having a D-serine dehydratase activity.   
     
     
         2 . The D-serine dehydratase according to  claim 1 , which does not react with L-serine. 
     
     
         3 . The D-serine dehydratase according to  claim 1 , wherein a reactivity to D-threonine is not more than 5% when a reactivity to D-serine is 100%. 
     
     
         4 . The D-serine dehydratase according to  claim 1 , which is a recombinant protein expressed in  Escherichia coli  as a host. 
     
     
         5 . A D-serine dehydratase gene comprising any of DNA selected from the group consisting of the following (A) to (C):
 (A) DNA encoding an amino acid sequence set forth in SEQ ID NO: 1;   (B) DNA having a base sequence set forth in SEQ ID NO: 2; and   (C) DNA having a base sequence homologous to the base sequence set forth in SEQ ID NO: 2 and encoding a protein having a D-serine dehydratase activity.   
     
     
         6 . A vector for expressing D-serine dehydratase, comprising a gene according  claim 5 . 
     
     
         7 . A transformant into which a gene according to  claim 5  is introduced. 
     
     
         8 . A production method for D-serine dehydratase, the method comprising steps of:
 (1) culturing the transformant according to  claim 7  in a condition in which a protein encoded by the gene is produced; and   (2) collecting the produced protein.   
     
     
         9 . A reagent for quantifying D-serine comprising the D-serine dehydratase according to  claim 1 . 
     
     
         10 . A kit for quantifying D-serine comprising a reagent for quantifying D-serine according to  claim 9  and an instruction. 
     
     
         11 . A D-serine quantification method comprising the following steps of:
 (1) preparing a reagent;   (2) adding D-serine dehydratase according to  claim 1  into the sample and reacting with each other;   (3) quantifying ammonia or pyruvic acid generated as a result of (2); and   (4) calculating an amount of D-serine in the sample from the quantified value obtained in (3).   
     
     
         12 . The D-serine quantification method according to  claim 11 , the method further comprising the following steps of:
 (5) adding amino acid racemase to a reaction solution after the step (2) and reacting with each other in a coexistence of the D-serine dehydratase;   (6) quantifying ammonia or pyruvic acid generated as a result of (5); and   (7) calculating a total amount of serine in the sample from the quantified value obtained in (6) and the amount of D-serine calculated in (4).   
     
     
         13 . A D-serine quantification method including the following steps of:
 (1) preparing a sample:   (2) adding the D-serine dehydratase according to  claim 1  to a part of the sample so as to react with each other;   (3) quantifying ammonia or pyruvic acid generated as a result of (2); and   (4) calculating an amount of serine in the sample from the quantified value obtained in (3);   (5) adding the D-serine dehydratase and amino acid racemase according to  claim 1  to another part of the sample and reacting with each other;   (6) quantifying ammonia or pyruvic acid generated as a result of (5); and   (7) calculating a total amount of serine in the sample from the quantified value obtained in (6).