Velikogne Stefan, Resch Verena, Dertnig Carina, Schrittwieser Joerg H, Kroutil Wolfgang
University of Graz Institute of Chemistry NAWI Graz, BioTechMed Graz Heinrichstrasse 28 8010 Graz Austria.
ChemCatChem. 2018 Aug 13;10(15):3236-3246. doi: 10.1002/cctc.201800607. Epub 2018 Jul 17.
Imine reductases (IREDs) have recently become a primary focus of research in biocatalysis, complementing other classes of amine-forming enzymes such as transaminases and amine dehydrogenases. Following in the footsteps of other research groups, we have established a set of IRED biocatalysts by sequence-based enzyme discovery. In this study, we present basic characterisation data for these novel IREDs and explore their activity and stereoselectivity using a panel of structurally diverse cyclic imines as substrates. Specific activities of >1 U/mg and excellent stereoselectivities (>99 %) were observed in many cases, and the enzymes proved surprisingly tolerant towards elevated substrate loadings. Co-expression of the IREDs with an alcohol dehydrogenase for cofactor regeneration led to whole-cell biocatalysts capable of efficiently reducing imines at 100 mM initial concentration with no need for the addition of extracellular nicotinamide cofactor. Preparative biotransformations on gram scale using these 'designer cells' afforded chiral amines in good yield and excellent optical purity.
亚胺还原酶（IREDs）最近已成为生物催化研究的主要焦点，对其他类型的胺形成酶如转氨酶和胺脱氢酶起到补充作用。跟随其他研究团队的脚步，我们通过基于序列的酶发现建立了一组IRED生物催化剂。在本研究中，我们展示了这些新型IREDs的基本表征数据，并使用一系列结构多样的环状亚胺作为底物探索了它们的活性和立体选择性。在许多情况下观察到了大于1 U/mg的比活性和优异的立体选择性（>99%），并且这些酶对提高的底物负载量表现出惊人的耐受性。IREDs与醇脱氢酶共表达以进行辅因子再生，产生了能够在100 mM初始浓度下有效还原亚胺的全细胞生物催化剂，无需添加细胞外烟酰胺辅因子。使用这些“定制细胞”进行克级规模的制备性生物转化，得到了高产率和优异光学纯度的手性胺。
