Ledent P, Frère J M
Laboratoire d'Enzymologie, Université de Liège, Sart-Tilman, Belgium.
Biochem J. 1993 Nov 1;295 ( Pt 3)(Pt 3):871-8. doi: 10.1042/bj2950871.
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.
研究了D类OXA2β-内酰胺酶对22种β-内酰胺抗生素的水解时间进程。其中，只有三种似乎符合整合的亨利-米氏方程。大多数青霉素、头孢菌素、氟氧头孢和亚胺培南观察到“爆发”动力学，这意味着存在分支途径。测定了一些底物水解不同阶段的动力学参数。通常用于解释这种涉及游离酶或酰基酶分支的可逆部分失活的机制，不足以解释酶的行为。亚胺培南的水解特征是出现两次“爆发”，而头孢硝噻吩的水解特征是部分底物诱导的失活，并伴有水解产物的竞争性抑制。
