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B6db references: 17259358

type Journal Article
authors Kim J, Kyung D, Yun H, Cho BK, Seo JH, Cha M, Kim BG
title Cloning and characterization of a novel beta-transaminase from Mesorhizobium sp. strain LUK: a new biocatalyst for the synthesis of enantiomerically pure beta-amino acids
journal Appl Environ Microbiol
Activity beta.transaminase
Family beta.transaminase
sel selected
ui 17259358
year (2007)
volume 73
number 6
pages 1772-82
abstract A novel beta-transaminase gene was cloned from Mesorhizobium sp. strain LUK. By using N-terminal sequence and an internal protein sequence, a digoxigenin-labeled probe was made for nonradioactive hybridization, and a 2.5-kb gene fragment was obtained by colony hybridization of a cosmid library. Through Southern blotting and sequence analysis of the selected cosmid clone, the structural gene of the enzyme (1,335 bp) was identified, which encodes a protein of 47,244 Da with a theoretical pI of 6.2. The deduced amino acid sequence of the beta-transaminase showed the highest sequence similarity with glutamate-1-semialdehyde aminomutase of transaminase subgroup II. The beta-transaminase showed higher activities toward d-beta-aminocarboxylic acids such as 3-aminobutyric acid, 3-amino-5-methylhexanoic acid, and 3-amino-3-phenylpropionic acid. The beta-transaminase has an unusually broad specificity for amino acceptors such as pyruvate and alpha-ketoglutarate/oxaloacetate. The enantioselectivity of the enzyme suggested that the recognition mode of beta-aminocarboxylic acids in the active site is reversed relative to that of alpha-amino acids. After comparison of its primary structure with transaminase subgroup II enzymes, it was proposed that R43 interacts with the carboxylate group of the beta-aminocarboxylic acids and the carboxylate group on the side chain of dicarboxylic alpha-keto acids such as alpha-ketoglutarate and oxaloacetate. R404 is another conserved residue, which interacts with the alpha-carboxylate group of the alpha-amino acids and alpha-keto acids. The beta-transaminase was used for the asymmetric synthesis of enantiomerically pure beta-aminocarboxylic acids. (3S)-Amino-3-phenylpropionic acid was produced from the ketocarboxylic acid ester substrate by coupled reaction with a lipase using 3-aminobutyric acid as amino donor.
last changed 2008/05/20 15:09

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