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Enhanced catalytic efficiency and enantioselectivity of epoxide hydrolase from Agrobacterium radiobacter AD1 by iterative saturation mutagenesis for (R)-epichlorohydrin synthesis

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Abstract

Enantioselective hydrolysis of epoxides by epoxide hydrolase (EH) is one of the most attractive approaches for the synthesis of chiral epoxides. So far, attempts to develop an efficient epoxide hydrolase -mediated biotransformation have been limited by either the low activity or insufficient enantioselectivity of epoxide hydrolase. In this study, iterative saturation mutagenesis (ISM) of epoxide hydrolase from Agrobacterium radiobacter AD1 (ArEH) was performed for efficient production of (R)-epichlorohydrin. Six amino acid residues, I108, A110, D131, I133, T247, and G245, were selected for site saturation mutagenesis, and a sequential combination of positive mutants using ISM was constructed. Targeted mutagenesis generated five mutants (T247K, I108L, D131S, T247K/I108L, and T247K/I108L/D131S) with improved activity and enantioselectivity. Kinetics analysis showed that the best mutant, T247K/I108L/D131S, exhibited a 4.5-fold higher catalytic efficiency (k cat/K m) value and a 2.1-fold higher enantioselectivity (E value) towards epichlorohydrin than the wild-type (WT) enzyme. Molecular docking computations support the source of notably improved enantioselectivity. In addition, the triple mutant also displayed a significantly enhanced thermostability, with > 8-fold longer half-life at 50 °C than WT. A gram-scale kinetic resolution of (R,S)-epichlorohydrin was performed using T247K/I108L/D131S mutant as biocatalyst, affording a (R)-epichlorohydrin yield of 40.2% (> 99.9% enantiomeric excess) and an average productivity of 1410 g L−1 d−1. The engineered T247K/I108L/D131S variant is a promising biocatalyst for the enzymatic synthesis of (R)-epichlorohydrin.

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Funding

This work was financially supported by the National Natural Science Foundation of China (grant number 21406205) and Natural Sciences Fund of Zhejiang Province (grant number Y17C050005).

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Correspondence to Yu-Guo Zheng.

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The authors declare that they have no conflict of interest.

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This article does not contain any studies with human participants or animals performed by any of the authors.

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Zou, SP., Zheng, YG., Wu, Q. et al. Enhanced catalytic efficiency and enantioselectivity of epoxide hydrolase from Agrobacterium radiobacter AD1 by iterative saturation mutagenesis for (R)-epichlorohydrin synthesis. Appl Microbiol Biotechnol 102, 733–742 (2018). https://doi.org/10.1007/s00253-017-8634-5

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  • DOI: https://doi.org/10.1007/s00253-017-8634-5

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