Mechanism of Stereospecific Production of L-Amino Acids from the Corresponding 5-Substituted Hydantoins by Bacillus brevis
The mechanism of stereospecific production of L-amino acids from the corresponding 5-substituted hydantoins by Bacillus brevis AJ-12299 was studied.The enzymes involved in the reaction were partially purified by DEAE-Toyopearl 650M column chromatography and their properties were investigated.The conversion of DL-5-substituted hydantoins to the corresponding L-amino acids consisted of the following two successive reactions.The first step was the ring-opening hydrolysis to N-carbamoyl amino acids catalyzed by an ATP dependent L-5-substituted hydantoin hydrolase.This reaction was stereospecific and the N-carbamoyl amino acid produced was exclusively the L-form.N-Carbamoyl-L-amino acid was also produced from the D-form of 5-substituted hydantoin, which suggests that spontaneous racemization occurred in the reaction mixture.In the second step, N-carbamoyl-L-amino acid was hydrolyzed to L-amino acid by an N-carbamoyl-L-amino acid hydrolase, which was also an L-specific enzyme.The ATP dependency of the L-5-substituted hydantoin hydrolase was supposed to be the limiting factor in the production of L-amino acids from the corresponding 5-substituted hydantoins by this bacterium.
Yamashiro, Akihiro,Kubota, Koji,Yokozeki, Kenzo
p. 2857 - 2864
(2007/10/02)
Enzymatic Production of L-Amino Acids from the Corresponding 5-Substituted Hydantoins by a Newly Isolated Bacterium, Bacillus brevis AJ-12299
A bacterium that stereospecifically produces L-valine from 5-isopropylhydantoin was isolated from soil.It was identified as Bacillus brevis and given the number AJ-12299.L-Valine productivity from L-, D- or DL-5-isopropylhydantoin by B. brevis AJ-12299 was rather low beacuse this bacterium had L-valine degrading-activity.In contrast, the productivity was improved by a mutant the L-valine degradation pathway of which was genetically blocked, and the 5-isopropylhydantoin consumed was stoichiometrically converted to L-valine.The optimal temperature and pH of the reaction were 30 deg C and 7.0 ca. 7.5.The enzyme involved in the reaction was inducible and was strongly induced by the addition of 5-isopropylhydantoin.In addition to L-valine production, this bacterium also produced various aliphatic and aromatic L-amino acids from the corresponding 5-substituted hydantoins.
Yamashiro, Akihiro,Yokozeki, Kenzo,Kano, Hideo,Kubota, Koji
p. 2851 - 2856
(2007/10/02)
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