Stereoselective Hydrolysis of Epoxides by re<i>Vr</i>EH3, a Novel Vigna radiata Epoxide Hydrolase with High Enantioselectivity or High and Complementary Regioselectivity

To provide more options for the stereoselective hydrolysis of epoxides, an epoxide hydrolase (<i>Vr</i>EH3) gene from Vigna radiata was cloned and expressed in Escherichia coli. Recombinant <i>Vr</i>EH3 displayed the maximum activity at pH 7.0 and 45 °C and high stability at pH 4.5–7.5 and 55 °C. Notably, re<i>Vr</i>EH3 exhibited high and complementary regioselectivity toward styrene oxides <b>1a</b>–<b>3a</b> and high enantioselectivity (<i>E</i> = 48.7) toward <i>o</i>-cresyl glycidyl ether <b>9a</b>. To elucidate these interesting phenomena, the interactions of the three-dimensional structure between <i>Vr</i>EH3 and enantiomers of <b>1a</b> and <b>9a</b> were analyzed by molecular docking simulation. Using E. coli/<i>vreh3</i> whole cells, gram-scale preparations of (<i>R</i>)-<b>1b</b> and (<i>R</i>)-<b>9a</b> were performed by enantioconvergent hydrolysis of 100 mM <i>rac</i>-<b>1a</b> and kinetic resolution of 200 mM <i>rac</i>-<b>9a</b> in the buffer-free water system at 25 °C. These afforded (<i>R</i>)-<b>1b</b> with >99% ee_p and 78.7% overall yield after recrystallization and (<i>R</i>)-<b>9a</b> with >99% ee_s, 38.7% overall yield, and 12.7 g/L/h space-time yield