Affiliation:
1. Laboratoire d'Enzymologie and Centre d'Ingéniérie des Proteines, Université de Liège, Institut de Chimie, B6, B-4000 Sart-Tilman (Liège 1), Belgium
Abstract
The hydrolysis time courses of 22 beta-lactam antibiotics by the class D OXA2 beta-lactamase were studied. Among these, only three appeared to correspond to the integrated Henri-Michaelis equation. ‘Burst’ kinetics, implying branched pathways, were observed with most penicillins, cephalosporins and with flomoxef and imipenem. Kinetic parameters characteristic of the different phases of the hydrolysis were determined for some substrates. Mechanisms generally accepted to explain such reversible partial inactivations involving branches at either the free enzyme or the acyl-enzyme were inadequate to explain the enzyme behaviour. The hydrolysis of imipenem was characterized by the occurrence of two ‘bursts’, and that of nitrocefin by a partial substrate-induced inactivation complicated by a competitive inhibition by the hydrolysis product.
Subject
Cell Biology,Molecular Biology,Biochemistry
Cited by
21 articles.
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