Inactivation of bacterial D-amino acid transaminase by beta-chloro-D-alanine.


Purified D-amino acid transaminase from Bacillus sphaericus catalyzes an alpha,beta elimination from the D isomer of beta-chloroalanine to yield equivalent amounts of pyruvate, chloride, and ammonia; the L isomer of chloroalanine is not a substrate for this transaminase. During the beta elimination there is a synchronous loss in enzyme activity; the Kinact for beta-chloroalanine was estimated to be about 10 micrometers. The alpha-aminoacrylate-Schiff base intermediate formed after beta elimination of chloride ion is probably the key intermediate that partitions between one inactivation event for every 1500 turnovers. In the presence of D-alanine and alpha-ketoglutarate, which are good substrates for the transaminase activity of this enzyme, beta-chloroalanine is a potent, competitive inhibitor (K1 = 10 micrometers) with D-alanine and a weak, uncompetitive inhibitor with alpha-ketoglutarate.

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@article{Soper1977InactivationOB, title={Inactivation of bacterial D-amino acid transaminase by beta-chloro-D-alanine.}, author={Thomas S. Soper and W M Jones and B Lerner and M. Trop and James Manning}, journal={The Journal of biological chemistry}, year={1977}, volume={252 10}, pages={3170-5} }