Properties of the Penicillin Deacylase Enzyme of Escherichia coli

Abstract

THE microbial enzyme which hydrolyses the side-chain from a penicillin to give 6-aminopenicillanic acid (6-APA) and carboxylic acid, or which catalyses the synthesis of penicillin from 6-APA and a carboxylic acid or its derivative, has been termed penicillin amidase^1–6, penicillin acylase⁷, benzylpenicillin acylase⁸, penicillin splitting and synthesizing enzyme^9,10 or acyl transferase¹¹. Investigations of the relative ease with which an enzyme from various sources will hydrolyse a series of penicillins has revealed the existence of at least two types of enzyme⁹, one hydrolysing phenoxymethylpenicillin much more readily than benzylpenicillin and the other hydrolysing benzylpenicillin much more readily than phenoxymethylpenicillin. Experiments on the hydrolysis of a series of penicillins with the Nocardia and Proteus enzymes⁸ have shown that the enzyme of these organisms has preference for a particular side-chain, namely, the phenylacetyl side-chain, and that all deviations from this structure cause reduction in enzyme activity. These reports indicate that substrate specificity is governed by the nature of the side-chain of the penicillin. Very little work has been done on the effect of structural modification of the acylated group on enzyme activity, but Huang, Seto and Shull⁸ do report that the use of the amide or ester of benzylpenicillin and phenoxymethylpenicillin or replacement of 6-APA by 7-aminocephalo-sporanic acid in various penicillins has only a minor effect on enzyme activity.