Cloning and characterization of a fish microsomal epoxide hydrolase of Danio rerio and application to kinetic resolution of racemic styrene oxide

Gene mining of the genome database of the zebra fish Danio rerio revealed the presence of a putative microsomal epoxide hydrolase (mEH)-like protein containing the characteristic catalytic triad composed of Asp223, Glu402, and His429 as well as the oxyanion hole common to all mEH. Based on the sequence information, a new EH gene was cloned by PCR amplification of cDNA of the zebra fish Danio rerio and expressed heterologously in Escherichia coli. The recombinant E. coli exhibited the enantiopreference toward (R)-styrene oxide with the maximum hydrolytic activity of 11.4 μmol min−1 (mg dcw)−1. When the kinetic resolution was conducted with 40 mM of racemic styrene oxide, enantiopure (S)-styrene oxide was obtained with an enantiomeric excess (ee) higher than 99 and 23.5% yield at 30 min. These results demonstrate that the recombinant fish EH has the possible application as a biocatalyst for the production of enantiopure epoxides.