Cress and Potato Soluble Epoxide Hydrolases: Purification, Biochemical Characterization, and Comparison to Mammalian Enzymes

Abstract Affinity chromatographic methods were developed for the one-step purification to homogeneity of recombinant soluble epoxide hydrolases (sEHs) from cress and potato. The enzymes are monomeric, with masses of 36 and 39 kDa and p I values of 4.5 and 5.0, respectively. In spite of a large difference in sequence, the two plant enzymes have properties of inhibition and substrate selectivity which differ only slightly from mammalian sEHs. Whereas mammalian sEHs are highly selective for trans - versus cis -substituted stilbene oxide and 1,3-diphenylpropene oxide (DPPO), plant sEHs exhibit far greater selectivity for trans - versus cis -stilbene oxide, but little to no selectivity for DPPO isomers. The isolation of a covalently linked plant sEH–substrate complex indicated that the plant and mammalian sEHs have a similar mechanism of action. We hypothesize an in vivo role for plant sEH in cutin biosynthesis, based on relatively high plant sEH activity on epoxystearate to form a cutin precursor, 9,10-dihydroxystearate. Plant sEHs display a high thermal stability relative to mammalian sEHs. This stability and their high enantioselectivity for a single substrate suggest that their potential as biocatalysts for the preparation of enantiopure epoxides should be evaluated.