Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, 10691, Stockholm, Sweden.
Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences and National Technology Innovation Center of Synthetic Biology, Tianjin, 300308, China.
ChemistryOpen. 2022 Jan;11(1):e202100250. doi: 10.1002/open.202100250. Epub 2021 Nov 25.
Imine reductases (IREDs) are NADPH-dependent enzymes (NADPH=nicotinamide adenine dinucleotide phosphate) that catalyze the reduction of imines to amines. They exhibit high enantioselectivity for a broad range of substrates, making them of interest for biocatalytic applications. In this work, we have employed density functional theory (DFT) calculations to elucidate the reaction mechanism and the origins of enantioselectivity of IRED from Amycolatopsis orientalis. Two substrates are considered, namely 1-methyl-3,4-dihydroisoquinoline and 2-propyl-piperideine. A model of the active site is built on the basis of the available crystal structure. For both substrates, different binding modes are first evaluated, followed by calculation of the hydride transfer transition states from each complex. We have also investigated the effect of mutations of certain important active site residues (Tyr179Ala and Asn241Ala) on the enantioselectivity. The calculated energies are consistent with the experimental observations and the analysis of transition states geometries provides insights into the origins of enantioselectivity of this enzyme.
亚胺还原酶（IREDs）是依赖 NADPH 的酶（NADPH=烟酰胺腺嘌呤二核苷酸磷酸），能够催化亚胺还原为胺。它们对广泛的底物表现出高对映选择性，因此它们在生物催化应用中很有意义。在这项工作中，我们使用密度泛函理论（DFT）计算阐明了来自东方拟无枝酸菌的 IRED 的反应机制和对映选择性的起源。考虑了两种底物，即 1-甲基-3,4-二氢异喹啉和 2-丙基-哌啶。基于可用的晶体结构构建了活性位点的模型。对于这两种底物，首先评估了不同的结合模式，然后从每个复合物计算了氢化物转移过渡态。我们还研究了某些重要活性位点残基（Tyr179Ala 和 Asn241Ala）突变对对映选择性的影响。计算的能量与实验观察结果一致，对过渡态几何形状的分析提供了对该酶对映选择性起源的深入了解。
