INTERACTION OF L-ASPARTATE BETA-DECARBOXYLASE WITH BETA-CHLORO-L-ALANINE . BETA-ELIMINATION REACTION WITH ACTIVE-SITE LABELING

L-Aspartate β-decarboxylase from Alcaligenes faecalis catalyzes the conversion of β-chloro-L-alanine into pyruvate, ammonia, and chloride ions. This reaction is accompanied by a slower reaction in which the enzyme becomes inactivated and in which the 3-carbon chain moiety of β-chloroalanine is covalently bound to the enzyme. Close to 1 mole of β-chloroalanine carbon is bound per 60,000 g of enzyme. The data indicate that about 30 % of the dialyzed alkylated enzyme is susceptible to decarboxylation by ceric sulfate and that about 20% to decarboxylation by ninhydrin indicating the presence of α-keto and α-amino acid derivatives, i.e., HOOCCOCH2-enzyme and HOOCCHNH2CH2-enzyme. Similar results were obtained when the enzyme was incubated with threo-β-chloro-L-α-aminobutyrate. Incubation of the apoenzyme or of the 4′-deoxypyridoxine 5′-phosphate-enzyme with β-chloroalanine does not lead to inactivation or binding. © 1969, American Chemical Society. All rights reserved.