Cress and potato soluble epoxide hydrolases: Purification, biochemical characterization, and comparison to mammalian enzymes

Affinity chromatographic methods were developed for the one-step purificati on to homogeneity of recombinant soluble epoxide hydrolases (sEHs) from cre ss and potato. The enzymes are monomeric, with masses of 36 and 39 kDa and pI values of 4.5 and 5.0, respectively. In spite of a large difference in s equence, the two plant enzymes have properties of inhibition and substrate selectivity which differ only slightly from mammalian sEHs. Whereas mammali an sEHs are highly selective for trans- versus cis-substituted stilbene oxi de and 1,3-diphenylpropene oxide (DPPO), plant sEHs exhibit far greater sel ectivity for transversus cis-stilbene oxide, but little to no selectivity f or DPPO isomers. The isolation of a covalently linked plant sEH-substrate c omplex indicated that the plant and mammalian sEHs have a similar mechanism of action. We hypothesize an in vivo role for plant sEH in cutin biosynthe sis, 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 enanti oselectivity for a single substrate suggest that their potential as biocata lysts for the preparation of enantiopure epoxides should be evaluated. (C) 2000 Academic Press.