In:
Applied and Environmental Microbiology, American Society for Microbiology, Vol. 73, No. 6 ( 2007-03-15), p. 1772-1782
Kurzfassung:
A novel β-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 β-transaminase showed the highest sequence similarity with glutamate-1-semialdehyde aminomutase of transaminase subgroup II. The β-transaminase showed higher activities toward d -β-aminocarboxylic acids such as 3-aminobutyric acid, 3-amino-5-methylhexanoic acid, and 3-amino-3-phenylpropionic acid. The β-transaminase has an unusually broad specificity for amino acceptors such as pyruvate and α-ketoglutarate/oxaloacetate. The enantioselectivity of the enzyme suggested that the recognition mode of β-aminocarboxylic acids in the active site is reversed relative to that of α-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 β-aminocarboxylic acids and the carboxylate group on the side chain of dicarboxylic α-keto acids such as α-ketoglutarate and oxaloacetate. R404 is another conserved residue, which interacts with the α-carboxylate group of the α-amino acids and α-keto acids. The β-transaminase was used for the asymmetric synthesis of enantiomerically pure β-aminocarboxylic acids. (3 S )-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.
Materialart:
Online-Ressource
ISSN:
0099-2240
,
1098-5336
DOI:
10.1128/AEM.02119-06
Sprache:
Englisch
Verlag:
American Society for Microbiology
Publikationsdatum:
2007
ZDB Id:
223011-2
ZDB Id:
1478346-0
SSG:
12
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