Stereospecific Hydration of cis- and trans-9,10-Epoxyoctadecanoic Acids

Biosynthesis of the C18 family of cutin acids. ι-Hydroxyoleic acid, ι-hydroxy-9,10-epoxystearic acid, 9,10,18-trihydroxystearic acid, and their Δ12-unsaturated analogs

“…As expected from such a reaction incorporation of oleic acid into cutin components by skin slices does indeed require molecular oxygen (data not shown). The epoxidation and hydration steps, besides being suggested by the experimental results presented in this paper, are also supported by the occurrence of chemically analogous reactions in other systems (Knoche, 1968(Knoche, , 1971Corey et al, 1966;van Tamelen et al, 1966;May and Abbott, 1973;Jerina et al, 1970;Kaubisch et al, 1972;Niehaus et al, 1970;Hartmann and Frear, 1963;Watabe et al, 1971;Watabe and Akamatsu, 1972;Oesch et al, 1971;Sims, 1971).…”

“…The minor cutin components, 9,18-and 10,18-dihydroxystearic acids, could arise either by hydration of co-hydroxyoleic acid or reduction of the corresponding epoxycutin acid. Since enzymes which catalyze hydration of olefins also catalyze hydration of epoxides in other biochemical systems (Niehaus et al, 1970;Albright and Schroepfer, 1971), it is possible that hydration of the 18-hydroxy-9,10-epoxystearic acid and 18-hydroxyoleic acid is catalyzed by the same (or similar) enzyme, giving rise to 9,10,18-trihydroxy stearic acid and 9,18-and/or 10,18-dihydroxystearic acids, respectively.…”

Hepatic epoxide hydrase. Structure-activity relations for substrates and inhibitors

“…Styrene and 1,2-dialin, the olefins corresponding to the substrate, styrene oxide, and the potent inhibitor, 1,2-epoxy-1,2,3,4-tetrahydronaphthalene, were tested as inhibitors and substrates. Weak inhibitions of 11 and 23%, respectively, were observed at 2 X 10"3 m. Hydration of these olefins to alcohols by epoxide hydrase in analogy to a bacterial enzyme which adds water to either olefins or epoxides (Niehaus et al, 1970) could not be detected by thin-layer chromatography. Cyclic ethers (tetrahydrofuran, dihydropyran, 1,8-epoxy-pmenthane, and furfuryl alcohol) had no significant effect on epoxide hydrase activity.…”

Enzyme-catalyzed allylic rearrangements

“…NRRL B-3266 catalyzes the interconversion of (Z)-9octadecenoic (oleic) acid, CE)-10-octadecenoic acid, and (R)-lO-hydroxyoctadecanoic acid.366-368 This same enzyme preparation also hydrates (E)-and (Z)-9,10-epoxyoctadecanoic acid. 369 As is the case with /3-hydroxydecanoyl thiol ester dehydrase, the isomerization is independent of the olefin hydration reaction; (Z)-9-and (E)-lO-octadecenoic acid are directly interconverted, and only (Z)-9-octadecenoic acid is a substrate for the hydration reactin'-COOH COOH Niehaus has cited several lines of evidence that point to the association of all three activities (isomerase, alkene hydratase, and epoxide hydrolase) with a single enzyme.370 (1) All of the activities are induced simultaneously when the organism is grown in the presence of oleate. (2) All three activities undergo thermal inactivation at the same rate, and the hydratase and isomerase activities are equally sensitive to inhibition by detergents.…”