Engineering an alcohol dehydrogenase with enhanced activity and stereoselectivity toward diaryl ketones: reduction of steric hindrance and change of the stereocontrol element
| Autor: | Lei Shao, Xiangguo Meng, Kai Wu, Rong Chen, Huang Jiankun, Zhijun Yang |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Steric effects
chemistry.chemical_classification Halogen bond biology 010405 organic chemistry Stereochemistry Chemistry Enantioselective synthesis 010402 general chemistry 01 natural sciences Catalysis 0104 chemical sciences Biocatalysis biology.protein Non-covalent interactions Stereoselectivity Alcohol dehydrogenase |
| Zdroj: | Catalysis Science & Technology. 10:1650-1660 |
| ISSN: | 2044-4761 2044-4753 |
| DOI: | 10.1039/c9cy02444a |
| Popis: | Steric hindrance in the binding pocket of an alcohol dehydrogenase (ADH) has a great impact on its activity and stereoselectivity simultaneously. Due to the subtle structural difference between two bulky phenyl substituents, the asymmetric synthesis of diaryl alcohols by bioreduction of diaryl ketones is often hindered by the low activity and stereoselectivity of ADHs. To engineer an ADH with practical properties and to investigate the molecular mechanism behind the asymmetric biocatalysis of diaryl ketones, we engineered an ADH from Lactobacillus kefiri (LkADH) to asymmetrically catalyse the reduction of 4-chlorodiphenylketones (CPPK), which are not catalysed by the wild type (WT) enzyme. Mutants seq1–seq5 with gradually increased activity and stereoselectivity were obtained through iterative “shrinking mutagenesis.” The final mutant seq5 (Y190P/I144V/L199V/E145C/M206F) demonstrated the highest activity and excellent stereoselectivity of >99% ee. Molecular simulation analyses revealed that mutations may enhance the activity by eliminating steric hindrance, inducing a more open binding loop and constructing more noncovalent interactions. The pro-R pose of CPPK with a halogen bond formed a pre-reaction conformation more easily than the pro-S pose, resulting in the high ee of (R)-CPPO in seq5. Moreover, different halogen bonds formed due to the different positions of chlorine substituents, resulting in opposite substrate binding orientation and stereoselectivity. Therefore, the stereoselectivity of seq5 was inverted toward ortho- rather than para-chlorine substituted ketones. These results indicate that the stereocontrol element of LkADH was changed to recognise diaryl ketones after steric hindrance was eliminated. This study provides novel insights into the role of steric hindrance and noncovalent bonds in the determination of the activity and stereoselectivity of enzymes, and presents an approach producing key intermediates of chiral drugs with practical potential. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|