Efficient biosynthesis of Vibegron intermediate using a novel carbonyl reductase based on molecular modification of hydrogen bonding network regulation

Abstract

Vibegron is a novel, potent, highly selective β₃-adrenergic receptor agonist for the treatment of overactive bladder with higher therapeutic capacity and lower side effects. Methyl(2S,3R)-2-((tert-butoxycarbonyl)amino)-3-hydroxy-3-phenylpropanoate ((2S,3R)-aminohydroxy ester) is a key chiral intermediate for the synthesis of Vibegron. A novel carbonyl reductase from Exiguobacterium sp. s126 (EaSDR6) was isolated using data mining technology from GenBank database with preferable catalytic activity. Hydrogen bond network regulation was performed using site-directed saturation mutagenesis and combination mutagenesis. The mutant EaSDR6^A138L/S193A was obtained with the activity improvement by 4.58 folds compared with the wild type EaSDR6. The K_m of EaSDR6^A138L/S193A was decreased from 1.57 mM to 0.67 mM, k_cat was increased by 2.17 folds, and the overall catalytic efficiency k_cat/K_m was increased by 5.07 folds. The organic-aqueous biphasic bioreaction system for the asymmetric synthesis of (2S,3R)-aminohydroxy ester was constructed for the first time. Under the substrate concentration of 150 g/L, the yield of (2S,3R)-aminohydroxy ester was > 99.99%, the e.e. was > 99.99%, and the spatiotemporal yield was 1.55 g/(L·h·g _DCW) after 12 h reaction. While the substrate concentration was increased to 200 g/L and the reaction lasted for 36 h, the yield of (2S,3R)-aminohydroxy ester was > 99.99%, the e.e. was > 99.99% and the spatiotemporal yield was 1.05 g/(L·h·g _DCW). The substrate concentration and spatiotemporal yield were higher than ever reported.

Keywords: Biphasic reaction system; Carbonyl reductase; Hydrogen bond network; Vibegron.