Hydrolysis of phenylacetanilides catalyzed by penicillin G acylase from Alcaligenes faecalis: Sensitivity of the reaction to substitution in the leaving group

The paper presents kinetic results on the hydrolysis of a series of p-substituted anilides catalyzed by penicillin G acylase from Alcaligenes faecalis. They are compared to the highly identical Escherichia coli enzyme and in combination with a structural model will contribute to deeper understanding of the catalytic mechanism and energetics of the reaction of the N-terminal-nucleophile superfamily. The Hammett plot indicates that acylation is the rate-limiting stage of hydrolysis. The collapse of the tetrahedral intermediate proceeds via synchronous bond breaking and formation, and the accumulation of charge on the amidic nitrogen due to the presence of a substituent is disfavored.