Proteolytic enzymes: studies of the hydrolysis of O-acetylserine peptides as models of the deacylation step

Abstract

The hydrolyses of N_α-benzyloxycarbonyl-L-histidyl-(O-acetyl)-L-serinamide and N_α-(quinoline-8-carbonyl)-O-acetyl-L-serinamide have been measured over a pH range. The former compound exhibits a pH dependenece with a plateau corresponding to general base catalysis by the imidazolyl function. The effective molarity of the general base catalysed reaction compared with the bimolecular analogue imidazole catalysed hydrolysis of N_αO-diacetyl-L-serinamide is 2.3M consistent with the results of other studies with intramolecular proton transfer reactions. The effect of general base catalysis concerted with intramolecular electrophilic assistance is shown not to be a major driving force in the hydrolysis of peptide models of acetylserine proteases.