A NOVEL ENZYMATIC DECARBOXYLATION PROCEEDS VIA A THIOL ESTER INTERMEDIATE

It is proposed that arylmalonate decarboxylase (AMDase)-catalyzed decarboxylation proceeds via a thiol ester intermediate. Kinetics and CD spectra indicated that alpha-bromophenylacetate is a competitive inhibitor. TOF mass data indicated that the inhibitor bound with the enzyme through a thiol ester bond which was formed between a cysteine residue of the enzyme and the carboxyl group of the inhibitor. This result was also supported by reactivation of the enzyme by the addition of 2-mercaptoethanol, which is expected to cleave the enzyme-inhibitor bond via nucleophilic attack on the thiol ester linkage.