棒酸对大肠杆菌RTEMβ-内酰胺酶灭活作用的动力学研究

Kinetic studies on the inactivation of Escherichia coli RTEM beta-lactamase by clavulanic acid.

作者信息

Fisher J, Charnas R L, Knowles J R

出版信息

Biochemistry. 1978 May 30;17(11):2180-4. doi: 10.1021/bi00604a024.

Abstract

The kinetic details of the irreversible inactivation of the Escherichia coli RTEM beta-lactamase by clavulanic acid have been elucidated. Clavulanate is destroyed by the enzyme and simultaneously inhibits it by producing two catalytically inactive forms. One of these is transiently stable and decomposes to free enzyme (k = 3.8 X 10(-3) S-1), while the other corresponds to an irreversibly inactivated form. The transient complex is formed from the Michaelis complex at a rate (k approximately 3 X 10(-2) S-1) which is some threefold faster than the rate of formation of the irreversibly inactivated complex. The transient complex is, therefore, the principle enzyme form present after short time periods. In the presence of excess clavulanate, however, all the enzyme accumulates into the irreversibly inactivated form. The number of clavulanate turnovers that occur prior to complete enzyme inactivation is 115.

摘要

棒酸对大肠杆菌RTEMβ-内酰胺酶不可逆失活的动力学细节已得到阐明。棒酸被该酶破坏，同时通过产生两种催化无活性的形式抑制该酶。其中一种形式短暂稳定，会分解为游离酶（k = 3.8×10⁻³ s⁻¹），而另一种形式则对应不可逆失活形式。瞬态复合物由米氏复合物以一定速率（k约为3×10⁻² s⁻¹）形成，该速率比不可逆失活复合物的形成速率快约三倍。因此，瞬态复合物是短时间后存在的主要酶形式。然而，在过量棒酸存在的情况下，所有酶都会积累为不可逆失活形式。在酶完全失活之前发生的棒酸周转数为115。