Development and characterization of recombinant whole cells expressing the soluble epoxide hydrolase of Danio rerio and its variant for enantioselective resolution of racemic styrene oxides

A recombinant soluble epoxide hydrolase (sEH) of zebra fish, Danio rerio, and its variant were developed and characterized. The variant consisted of five-point mutations such as Glu88Arg, Thr102Ala, Met368Ile, Lys398Glu and Gly412Asp. The catalytically important amino acids of Asp331, Tyr379, Tyr460, Asp496 and His524 were determined to be highly conserved in both of the sEHs, on the basis of multiple sequence alignment and homology modeling. The enantiomeric ratio of the variant sEH was 1.43-fold higher than that of the wild-type sEH. Interestingly, both of the sEH and its variant possessed (S)-styrene oxide-preferred hydrolytic activity, while the microsomal EH (mEH) of D. rerio exhibited the enantiopreference toward (R)-enantiomer, indicating that (R)- and (S)-styrene oxide could be prepared by using sEH and mEH, respectively. (R)-Styrene oxide with high enantiopurity of 99%ee could be obtained by the enantioselective hydrolysis activities of the recombinant Escherichia coli whole cells expressing the wild-type and variant sEHs of D. rerio.