Mechanistic Study of the Reaction of Thiol-Containing Enzymes with α,β-Unsaturated Carbonyl Substrates by Computation and Chemoassays
Mechanistic Study of the Reaction of Thiol-Containing Enzymes with α,β-Unsaturated Carbonyl Substrates by Computation and Chemoassays
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DOI：
10.1002/cmdc.201000020
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发表时间：
2010-06-01
期刊：
影响因子：
3.4
通讯作者：
Engels, Bernd
中科院分区：
文献类型：
--
作者：
Paasche, Alexander;Schiller, Markus;Engels, Bernd
我们研究了取代的α，β-不饱和羰基化合物（迈克尔系统）和硫醇之间的反应，通过计算以及化学分析。结果提供洞察的替代模式的函数的基本机制的变化。这对于依他尼酸衍生物抑制SARS冠状病毒主要蛋白酶（SARS-CoV M-pro）的机制以及取代的α，β-不饱和羰基化合物的过量毒性是感兴趣的。本研究比较了可能的反应过程，包括1，4-加成，然后是酮化步骤，并强调了碱催化步骤的重要性，巯基在酶的反应性。迈克尔体系中的苯基和甲基取代基降低了亲电化合物的反应活性，但氯苯基取代基部分恢复了反应活性。计算还表明，推电子取代基导致反应机理的变化。迈克尔系统的构象也被发现显着影响反应性：S-顺式构象导致比S-反式构象更高的反应性。计算的数据解释了取代的α，β-不饱和羰基化合物和化学测定中的反应速率的测量抑制效力的趋势。它们还表明，抑制的可逆性并不与抑制剂和蛋白酶之间形成新的共价键相反。
We investigated the reactions between substituted alpha,beta-unsaturated carbonyl compounds (Michael systems) and thiols by computations as well as chemoassays. The results give insight into variations in the underlying mechanisms as a function of the substitution pattern. This is of interest for the mechanisms of inhibition of the SARS coronavirus main protease (SARS-CoV M-pro) by etacrynic acid derivatives as well as for the excess toxicity of substituted alpha,beta-unsaturated carbonyl compounds. This study compares possible reaction courses including 1,4-addition followed by a ketonization step, and underscores the importance of a base-catalyzed step for the reactivity of thiol groups in enzymes. Phenyl and methyl substituents at the Michael system decrease the reactivity of the electrophilic compound, but chlorophenyl substituents partly recover the reactivity. Computations also indicate that electron-pushing substituents lead to a change in the reaction mechanism. The conformation of the Michael system is also found to significantly influence reactivity: the s-cis conformation leads to higher reactivity than the s-trans conformation. The computed data explain the trends in measured inhibition potencies of substituted alpha,beta-unsaturated carbonyl compounds and of reaction rates in chemical assays. They also indicate that the reversibility of inhibition does not stand in contrast to the formation of a new covalent bond between inhibitor and protease.