Why does the G117H mutation considerably improve the activity of human butyrylcholinesterase against sarin? Insights from quantum mechanical/molecular mechanical free energy calculations.
Why does the G117H mutation considerably improve the activity of human butyrylcholinesterase against sarin? Insights from quantum mechanical/molecular mechanical free energy calculations.
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为什么G117H突变会大大改善人丁乙酸酯酶对Sarin的活性？量子机械/分子机械自由能计算的见解。
DOI：
10.1021/bi3009246
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发表时间：
2012-11-06
期刊：
影响因子：
2.9
通讯作者：
Zhan CG
中科院分区：
文献类型：
--
作者：
Yao Y;Liu J;Zhan CG
人丁酰胆碱酯酶(BChE)被认为是最有前途的有机磷(OP)战神经毒剂生物清除剂。人BChE的G117H突变体已被鉴定为一种潜在的催化生物清除剂，对沙林等OP神经毒剂具有显著的活性，但仍不能满足临床应用。为了进一步设计针对OP神经毒剂的高活性突变体，了解G117H突变如何提高活性是至关重要的。通过第一性原理量子力学/分子机械自由能(QM/MM-FE)计算，探讨了沙林磷酸化野生型BChE及其突变体G117H自发再激活的反应机理和自由能谱，阐明了G117H突变对活性的显著影响。对于野生型和G117H突变酶，H438作为启动自发再激活的通用碱基，包括两个反应步骤：水分子对磷的亲核攻击和五配位磷中间体的分解。对于野生型和G117H突变体，计算的总自由能垒分别为30.2和23.9kcal/mol，与已有的实验动力学数据符合得很好。根据计算结果，突变残基(G117H突变体中的H117)不能作为一般碱基启动自发再激活。相反，它扭曲了氧阴离子空穴，使磷对亲核水分子更加开放，导致速率决定步骤显著改变，显著提高了人BChE的催化活性。
Human butyrylcholinesterase (BChE) is recognized as the most promising bioscavenger for organophosphorus (OP) warfare nerve agents. The G117H mutant of human BChE has been identified as a potential catalytic bioscavenger with a remarkably improved activity against OP nerve agents such as sarin, but it still does not satisfy the clinical use. For further design of the higher-activity mutants against OP nerve agents, it is essential to understand how the G117H mutation improves the activity. The reaction mechanisms and the free energy profiles for spontaneous reactivation of the wild-type BChE and its G117H mutant phosphorylated by sarin have been explored, in this study, by performing first-principles quantum mechanical/molecular mechanical free energy (QM/MM-FE) calculations, and the remarkable role of the G117H mutation on the activity has been elucidated. For both the wild-type and G117H mutant enzymes, H438 acts as a general base to initiate the spontaneous reactivation which consists of two reaction steps: the nucleophilic attack at the phosphorus by a water molecule and decomposition of the pentacoordinated phosphorus intermediate. The calculated overall free energy barriers, i.e. 30.2 and 23.9 kcal/mol for the wild-type and G117H mutant, respectively, are in good agreement with available experimental kinetic data. Based on the calculated results, the mutated residue (H117 in the G117H mutant) cannot initiate the spontaneous reactivation as a general base. Instead, it skews the oxyanion hole and makes the phosphorus more open to the nucleophilic water molecule, resulting in remarkable change of the rate-determining step and significantly improved catalytic activity of human BChE.
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影响因子：
5.1
作者：
Broomfield, CA;Lockridge, O;Millard, CB
通讯作者：
Millard, CB
影响因子：
15
作者：
Koca, J;Zhan, CG;Ornstein, RL
通讯作者：
Ornstein, RL
DOI：
10.1021/jp9055335
发表时间：
2009-12-17
期刊：
The journal of physical chemistry. B
影响因子：
--
作者：
Liu J;Zhang Y;Zhan CG
通讯作者：
Zhan CG
影响因子：
4.4
作者：
JORGENSEN, WL;CHANDRASEKHAR, J;KLEIN, ML
通讯作者：
KLEIN, ML
影响因子：
15
作者：
Cheng, YH;Zhang, YK;McCammon, JA
通讯作者：
McCammon, JA