Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 10691, Stockholm, Sweden.
Chemistry. 2019 Sep 12;25(51):11945-11954. doi: 10.1002/chem.201902351. Epub 2019 Aug 21.
Acyl transferase from Mycobacterium smegmatis (MsAcT) is a promising biocatalyst because it catalyzes an acyl transfer reaction in aqueous solution, thereby accepting many primary and secondary alcohols as substrates. MsAcT also exhibits high enantioselectivity for a selected number of secondary alcohols. To increase the applicability of this enzyme for the production of optically active compounds, a detailed understanding of the reaction mechanism and the factors that affect enantioselectivity is essential. Herein, quantum chemical calculations are employed to study the reactions of two secondary alcohols, 1-isopropyl propargyl alcohol and 2-hydroxy propanenitrile, for which the enzyme displays opposite enantiopreference, favoring the S enantiomer in the former case and R enantiomer in the latter. A model of the active site has been designed and for both substrates various binding modes are evaluated and the intermediates and transition states along the reaction path are then located. The calculated energy profiles agree with the experimental observations, and reproduce the selectivity outcome. Through a detailed analysis of the geometries of key transition states, insights into the origins of the enantiopreference are obtained.
来自耻垢分枝杆菌（Mycobacterium smegmatis）的酰基转移酶（MsAcT）是一种很有前途的生物催化剂，因为它可以在水溶液中催化酰基转移反应，从而接受许多伯醇和仲醇作为底物。MsAcT 对一些特定的仲醇也表现出高对映选择性。为了增加这种酶在生产光学活性化合物方面的适用性，详细了解反应机制和影响对映选择性的因素是至关重要的。在此，我们采用量子化学计算研究了两种仲醇的反应，1-异丙基丙炔醇和 2-羟基丙腈，对于这两种醇，酶表现出相反的对映体偏好，前者有利于 S 对映体，后者有利于 R 对映体。设计了一个活性位点模型，并对两种底物的各种结合模式进行了评估，然后找到了反应路径上的中间体和过渡态。计算得到的能量曲线与实验观察结果一致，并重现了选择性结果。通过对关键过渡态的几何形状进行详细分析，我们获得了对映体偏好的起源的深入了解。
