The catalytic mechanism of S-acyltransferases: acylation is triggered on by a loose transition state and deacylation is turned off by a tight transition state
The catalytic mechanism of S-acyltransferases: acylation is triggered on by a loose transition state and deacylation is turned off by a tight transition state
复制标题
S-酰基转移酶的催化机制：松散过渡态触发酰化，紧密过渡态关闭脱酰化
DOI：
10.1039/c9cp02248a
复制
发表时间：
2019
影响因子：
3.3
通讯作者：
Jianzhuang Yao
中科院分区：
文献类型：
--
作者：
Xia Wang;Grace Mercure Bakanina Kissanga;E. Li;Qiang Li;Jianzhuang Yao
由S-酰基转移酶催化的动态蛋白S-棕榈酰化是一种基本的翻译后修饰，不仅参与了一系列重要的细胞过程，而且参与了一系列与人类健康和疾病相关的问题(如大脑发育和行为、免疫反应调节、肿瘤抑制和癌症)。有趣的是，人S-酰基转移酶已被认为是治疗癌症的一个有前途的药物靶点。尽管S-酰基转移酶具有重要意义，但其基本催化机制仍不清楚。在这项研究中，我们进行了大量的模拟和计算来描述人S-酰基转移酶催化自酰化的基本机理，揭示了一个具有松散过渡态特征的一步反应途径。由于具有相当高的自由能垒，避免了具有紧密过渡态的脱酰化过程。这种特殊的催化机制对于保护棕榈酰化的酶免受水分子的不必要的水解是必要的，因为紧密过渡态积累的负电荷不能有效地被氧阴离子空穴的弱氢键稳定。预测了人S-酰基转移酶催化自酰化反应的激活自由能垒为17.8kcal·−-1，与根据传统过渡态理论得到的激活自由能垒为18.5kcal·moL·−-1很好地吻合，表明计算结果是有效的。这些机理上的见解(例如详细的催化机制和过渡态的性质)不仅有助于癌症治疗的合理药物发现(例如过渡态类似物的设计)和具有所需酰基-CoA特异性的工程S酰基转移酶的设计，而且还将有助于未来对其他S-酰基转移酶催化机制的研究。
Dynamic protein S-palmitoylation catalyzed by S-acyltransferases is one of the fundamental post-translational modifications involved not only in a wide range of vital cellular processes but also in a series of human health and diseases-related issues (such as brain development and behavior, immune response regulation, tumor suppressor, and cancer). Interestingly, human S-acyltransferase has been recognized as a promising drug-target for cancer treatment. Despite the prominent importance, the fundamental catalytic mechanism of S-acyltransferases remains elusive. In this study, we performed extensive simulations and calculations to describe the fundamental catalytic mechanism of autoacylation catalyzed by human S-acyltransferase, revealing a single-step reaction pathway characterized by a loose transition state. The deacylation process with a tight transition state is avoided due to the substantially high free energy barrier. This specific catalytic mechanism is necessary to protect palmitoylated-enzymes from unwanted hydrolysis by water molecules since the accumulated negative charge of the tight transition state cannot be effectively stabilized by the weak hydrogen bond of the oxyanion hole. The activation free energy barrier of the autoacylation catalyzed by human S-acyltransferase was predicted to be 17.8 kcal mol−1, which is in good agreement with the experimentally derived activation free energy barrier (18.5 kcal mol−1) based on the conventional transition state theory, suggesting the validity of the computational results. The mechanistic insights (e.g., detailed catalytic mechanism and the nature of the transition state) are expected to do good not only to rational drug discovery (e.g., design of transition state analogues) toward cancer treatment and the design of engineered S-acyltransferases with desired acyl-CoA specificity but also to future studies on the catalytic mechanisms of other S-acyltransferases.