Ramsay R R, Koerber S C, Singer T P
Biochemistry. 1987 Jun 2;26(11):3045-50. doi: 10.1021/bi00385a015.
The kinetic mechanism of monoamine oxidase B involves either a binary or a ternary complex, depending on the substrate. In this study, stopped-flow kinetic data provide direct evidence for ternary complexes not only of reduced enzyme, oxygen, and product but also of reduced enzyme, oxygen, and substrate, both for benzylamine and for the tertiary amine 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). However, the mechanism for a given substrate is not exclusive but, rather, is determined by competition between the alternate pathways as a result of different rate constants for the oxidation of the reduced enzyme, the reduced enzyme-product complex, and the reduced enzyme-substrate complex, as well as the different dissociation constants for the complexes. Comparison of the rate constants obtained from the stopped-flow studies with steady-state data indicates that the overall rate of reaction for the oxidation of MPTP by monoamine oxidase is dominated by the reductive step, but for benzylamine the steady-state rate is determined by a complex function of the rates of both the reductive and oxidative half-reactions.
单胺氧化酶B的动力学机制涉及二元或三元复合物，这取决于底物。在本研究中，停流动力学数据不仅为还原型酶、氧气和产物形成的三元复合物，而且为还原型酶、氧气和底物形成的三元复合物提供了直接证据，这两种情况分别针对苄胺和叔胺1-甲基-4-苯基-1,2,3,6-四氢吡啶（MPTP）。然而，给定底物的机制并非唯一的，而是由还原型酶、还原型酶-产物复合物和还原型酶-底物复合物氧化的不同速率常数以及复合物的不同解离常数导致的交替途径之间的竞争所决定。将停流研究获得的速率常数与稳态数据进行比较表明，单胺氧化酶氧化MPTP的总反应速率由还原步骤主导，但对于苄胺，稳态速率由还原和氧化半反应速率的复杂函数决定。
