Exploring the Biocatalytic Scope of a Novel Enantioselective Halohydrin Dehalogenase from an Alphaproteobacterium
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A gene encoding halohydrin dehalogenase from an alphaproteobacterium (AbHHDH) was identified, cloned and over-expressed in Escherichia coli. AbHHDH was able to catalyze the stereoselective dehalogenation of prochiral and racemic halohydrins. It showed the highest enantioselectivity in the dehalogenation of 20 mM (R,S)-2-bromo-1-phenylethanol, which yielded (S)-2-bromo-1-phenylethanol with 99% ee and 34.5% yield. Moreover, AbHHDH catalyzed the azidolysis of epoxides with low to moderate (S)-enantioselectivity. The highest enantioselectivity (E = 18.6) was observed when (R,S)-benzyl glycidyl ether was used as the substrate. A sequential kinetic resolution catalyzed by HHDH was employed for the synthesis of chiral 1-chloro-3-phenoxy-2-propanol. We prepared enantiopure (S)-isomer with a high enantiopurity of ee > 99% and a yield of 30.7% (E-value: 21.3) by kinetic resolution of 20 mM substrate. The (S)-isomer with 99% ee readily obtained from 40 to 150 mM (R,S)-1-chloro-3-phenoxy-2-propanol. Taken together, the results of this study demonstrate the applicability of this HHDH for the production of optically active compounds.
KeywordsHalohydrin dehalogenase Epoxides Halohydrins Enantioselectivity Biocatalysis
This project was sponsored by the National Natural Science Foundation of China (No. 21606192), the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (No. 16KJB180029) and the China Postdoctoral Science Foundation (No. 2016M601795).
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Conflict of interest
The authors declared that they have no conflicts of interest to this work.
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