Download MendeleyStructural Insight into Enantioselective Inversion of an Alcohol Dehydrogenase Reveals a "Polar Gate" in Stereorecognition of Diaryl Ketones.
Zhou, J.Y., Wang, Y., Xu, G.C., Wu, L., Han, R.Z., Schwaneberg, U., Rao, Y.J., Zhao, Y.L., Zhou, J.H., Ni, Y.(2018) J Am Chem Soc 140: 12645-12654
- PubMed: 30247889
- DOI: https://doi.org/10.1021/jacs.8b08640
- Primary Citation of Related Structures:
5Z2X, 5ZEC, 5ZED - PubMed Abstract:
Diaryl ketones are important building blocks for synthesizing pharmaceuticals and are generally regarded as "difficult-to-reduce" ketones due to the large steric hindrance of their two bulky aromatic side chains. Alcohol dehydrogenase from Kluyveromyces polyspora ( KpADH) has been identified as a robust biocatalyst due to its high conversion of diaryl ketone substrate (4-chlorophenyl)(pyridine-2-yl)ketone (CPMK) with a moderate R-selectivity of 82% ee. To modulate the stereoselectivity of KpADH, a "polarity scanning" strategy was proposed, in which six key residues inside and at the entrance of the substrate binding pocket were identified. After iterative combinatorial mutagenesis, variants Mu-R2 and Mu-S5 with enhanced (99.2% ee, R) and inverted (97.8% ee, S) stereoselectivity were obtained. The crystal structures of KpADH and two mutants in complex with NADPH were resolved to elucidate the evolution of enantioselective inversion. Based on MD simulation, Mu-R2-CPMK ProR and Mu-S5-CPMK ProS were more favorable in the formation of prereaction states. Interestingly, a quadrilateral plane formed by α-carbons of four residues (N136, V161, C237, and G214) was identified at the entrance of the substrate binding pocket of Mu-S5; this plane acts as a "polar gate" for substrates. Due to the discrepancy in charge characteristics between chlorophenyl and pyridine substituents, the pro- S orientation of CPMK is defined when it passes through the "polar gate" in Mu-S5, whereas the similar plane in wild-type is blocked by several aromatic residues. Our result paves the way for engineering stereocomplementary ADH toward bulky diaryl ketones and provides structural insight into the mechanism of stereoselective inversion.
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology , Jiangnan University , Wuxi , 214122 Jiangsu , China.
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