This report describes a double-exponential algebraic equation for the time course of irreversible enzyme inhibition following the two-step mechanism E + I <==> E.I ---> EI under the steady-state approximation. Under the previously invoked rapid-equilibrium approximation [Kitz & Wilson (1962) J. Biol. Chem. 237, 3245] it was assumed that the rate constant for the reversible dissociation of the initial noncovalent complex is very much faster than the rate constant for the irreversible inactivation step. The steady-state algebraic equation reported here removes any restrictions on the relative magnitude of microscopic rate constants. The resulting formula was used in heuristic simulations designed to test the performance of the standard rapid-equilibrium kinetic model. The results show that if the inactivation rate constant is significantly higher than the dissociation rate constant, the conventional "kobs" method is incapable of correctly distinguishing between the two-step inhibition mechanism and a simpler one-step variant, E + I ---> EI, even for inhibitors that have very high binding affinity in the reversible noncovalent step.

中文翻译：

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抑制共价酶的时间过程的稳态代数模型

该报告描述了在稳态近似下遵循两步机制E + I <= EI ---> EI的不可逆酶抑制的时间过程的双指数代数方程。在先前援引的快速平衡近似下[Kitz＆Wilson（1962）J. Biol。化学 [237，3245]假定初始非共价复合物可逆解离的速率常数比不可逆灭活步骤的速率常数快得多。这里报道的稳态代数方程式消除了对微观速率常数的相对大小的任何限制。所得公式用于启发式仿真中，旨在测试标准快速平衡动力学模型的性能。