Clarification of penicillin G acylase reaction mechanism

The kinetics of the enzymic reaction of penicillin G acylase from a mutant of Escherichia coli ATCC 11105 in forward and reverse directions were studi ed and the kinetic constants determined. Results show that the enzyme is in hibited by excess substrate, penicillin G (Pen G), and by both products. Th e non-competitive inhibition by 6-aminopenicillanic acid (B-APA) and compet itive inhibition by phenylacetic acid were observed for the ordered uni bi deacylation reaction in the forward direction. The optimum pH value for the reverse acylation reaction was 5.7. The bi uni mechanism for the reverse r eaction was investigated and the inhibitory effects of the substrates, 6-AP A and phenyl acetic acid, and the product, Pen G, were studied. Result show s that Pen G is the mixed-type inhibitor for the reverse reaction. (C) 2001 Elsevier Science Ltd. All rights reserved.