Structural Biochemistry, Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
Industrial Organic Chemistry and Biotechnology, Faculty of Chemistry, Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.
Biomolecules. 2020 Jul 31;10(8):1130. doi: 10.3390/biom10081130.
NADPH-dependent imine reductases (IREDs) are enzymes capable of enantioselectively reducing imines to chiral secondary amines, which represent important building blocks in the chemical and pharmaceutical industry. Since their discovery in 2011, many previously unknown IREDs have been identified, biochemically and structurally characterized and categorized into families. However, the catalytic mechanism and guiding principles for substrate specificity and stereoselectivity remain disputed. Herein, we describe the crystal structure of -IRED- from together with its cofactor NADPH. -IRED- belongs to the -enantioselective superfamily 3 (SFam3) and is the first IRED from SFam3 to be structurally described. The data presented provide further evidence for the overall high degree of structural conservation between different IREDs of various superfamilies. We discuss the role of Asp170 in catalysis and the importance of hydrophobic amino acids in the active site for stereospecificity. Moreover, a separate entrance to the active site, potentially functioning according to a gatekeeping mechanism regulating access and, therefore, substrate specificity is described.
NADPH 依赖的亚胺还原酶（IREDs）是能够对映选择性地将亚胺还原为手性仲胺的酶，仲胺是化学和制药工业中的重要构建块。自 2011 年发现以来，已经鉴定出许多以前未知的 IRED，并对其进行了生物化学和结构表征，并进行了分类。然而，催化机制以及指导底物特异性和对映选择性的原则仍存在争议。本文描述了来自 的 -IRED- 的晶体结构及其辅因子 NADPH。-IRED 属于 -enantioselective superfamily 3（SFam3），是第一个被结构描述的 SFam3 IRED。所提供的数据进一步证明了不同超家族的不同 IRED 之间整体结构高度保守。我们讨论了 Asp170 在催化中的作用以及活性位点中疏水性氨基酸对立体特异性的重要性。此外，还描述了活性位点的单独入口，根据调控进入的“门卫”机制，该入口可能具有功能，因此可以调节底物特异性。
