Knott-Hunziker V, Orlek B S, Sammes P G, Waley S G
Biochem J. 1980 Jun 1;187(3):797-802. doi: 10.1042/bj1870797.
The kinetics of the inactivation of beta-lactamase I from Bacillus cereus 569 by preparations of 6 alpha-bromopenicillanic acid showed unexpected features. These can be quantitatively accounted for on the basis of the inactivator being the epimer, 6 beta-bromopenicillanic acid. At pH 9.2, the rate-determining step in the inactivation is the formation of the inactivator. When pure 6 beta-bromopenicillanic acid is used to inactivate beta-lactamase I, simple second-order kinetics are observed. The inactivated enzyme has a new absorption peak at 326 nm. The rate constant for inactivation has the same value as the rate constant for appearance of absorption at 326 nm; the rate-determining step may thus be fission of the beta-lactam ring of 6 beta-bromopenicillanic acid. Inactivation is slower in the presence of substrate, and the observed kinetics can be quantitatively accounted for on a simple competitive model. The results strongly suggest that inactivation is a consequence of reaction at the active site.
蜡样芽孢杆菌569的β-内酰胺酶I被6α-溴青霉烷酸制剂灭活的动力学表现出意外的特征。这些特征可以基于灭活剂是差向异构体6β-溴青霉烷酸来进行定量解释。在pH 9.2时，灭活过程中的速率决定步骤是灭活剂的形成。当使用纯的6β-溴青霉烷酸来灭活β-内酰胺酶I时，观察到简单的二级动力学。失活的酶在326nm处有一个新的吸收峰。灭活的速率常数与326nm处吸收出现的速率常数具有相同的值；因此，速率决定步骤可能是6β-溴青霉烷酸的β-内酰胺环的裂开。在底物存在下灭活较慢，并且观察到的动力学可以在简单的竞争模型上进行定量解释。结果强烈表明灭活是活性位点反应的结果。
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