Mu Xia, Zhang Chunchun, Xu Dingguo
MOE Key Laboratory of Green Chemistry, College of Chemistry, Sichuan University, Chengdu, Sichuan, 610064, People's Republic of China.
Analytical & Testing Center, Sichuan University, Chengdu, Sichuan, 610064, People's Republic of China.
J Mol Model. 2016 Jun;22(6):132. doi: 10.1007/s00894-016-3004-2. Epub 2016 May 16.
Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II and degrades bradykinin and other vasoactive peptides. ACE inhibitors are used to treat diseases such as hypertension and heart failure. It is thus highly desirable to understand the catalytic mechanism of ACE, as this should facilitate the design of more powerful and selective ACE inhibitors. ACE exhibits two different active domains, the C-domain and the N-domain. In this work, we systematically investigated the inhibitor- and substrate-binding patterns in the N-domain of human ACE using a combined quantum mechanical and molecular mechanical approach. The hydrolysis of hippuryl-histidyl-leucine (HHL) as catalyzed by the N-domain of human somatic ACE was explored, and the effects of chloride ion on the overall reaction were also investigated. Two models, one with and one without a chloride ion at the first binding position, were then designed to examine the chloride dependence of inhibitor-substrate binding and the catalytic mechanism. Our calculations indicate that the hydrolysis reaction follows a stepwise general base/general acid catalysis path. The estimated mean free energy barrier height in the two models is about 15.6 kcal/mol, which agrees very well with the experimentally estimated value of 15.8 kcal/mol. Our simulations thus suggest that the N-domain is in a mixed form during ACE-catalyzed hydrolysis, with the single-chloride-ion and the double-chloride-ion forms existing simultaneously. Graphical Abstract Superposition of ACE C- and N- domains.
血管紧张素转换酶（ACE）将血管紧张素I转化为血管紧张素II，并降解缓激肽和其他血管活性肽。ACE抑制剂用于治疗高血压和心力衰竭等疾病。因此，非常有必要了解ACE的催化机制，因为这将有助于设计更强大、更具选择性的ACE抑制剂。ACE具有两个不同的活性结构域，即C结构域和N结构域。在这项工作中，我们采用量子力学和分子力学相结合的方法，系统地研究了人ACE的N结构域中抑制剂和底物的结合模式。探索了人体细胞ACE的N结构域催化的马尿酰-组氨酰-亮氨酸（HHL）的水解反应，并研究了氯离子对整个反应的影响。然后设计了两个模型，一个在第一个结合位置有氯离子，另一个没有，以研究抑制剂-底物结合对氯离子的依赖性和催化机制。我们的计算表明，水解反应遵循逐步的广义碱/广义酸催化路径。两个模型中估计的平均自由能垒高度约为15.6千卡/摩尔，与实验估计值15.8千卡/摩尔非常吻合。因此，我们的模拟表明，在ACE催化的水解过程中，N结构域处于混合形式，单氯离子和双氯离子形式同时存在。图形摘要ACE C结构域和N结构域的叠加。
