A NEW-TYPE OF CARBOXYPEPTIDASE-A INHIBITOR - DESIGN, SYNTHESIS, AND MECHANISTIC IMPLICATION

2-Benzyl-3,4-epoxybutanoic acid (BEBA) which was designed rationally a s an irreversible inhibitor of carboxypeptidase A on the basis of the known topology of the active site and catalytic mechanism of the enzym e indeed inactivated the enzyme very efficiently with a covalent modif ication at the carboxylate of Glu-270. The partition ratio of BEBA was determined to be 20.3. Of four stereoisomers of BEBA, (2S, 3R)- and ( 2R, 3S)-BEBA show the inhibitory activity, and the other two isomers a re essentially inactive. This stereospecificity of BEBA in the inhibit ion was explained with a proposition of a three-dimensional representa tion of the active site of the enzyme. All four stereoisomers were syn thesized effectively and conveniently starting with optically active 2 -benzyl-2-vinylacetic acid which was obtained by a kinetic resolution of racemic methyl ester of the acid using alpha-chymotrypsin.