Epoxidation of cis and trans Δ9‐unsaturated lauric acids by a cytochrome P‐450‐dependent system from higher plant microsomes

Abstract
A new epoxygenase, differing in substrate and stereospecificity from those previously described in mammals, bacteria and Vicia faba, has been characterized in higher plants. A microsomal fraction from Jerusalem artichoke tubers which catalyses in‐chain monohydroxylation of lauric acid has now been found to convert synthetic 9‐dodecenoic acid (9‐DDNA) to 9,10‐epoxylauric acid. Epoxidation of the cis and trans isomers proceeds at similar rates affording the corresponding cis and trans epoxides. This reaction is dependent upon O2 and NADPH and does not occur with boiled microsomes. Lauric acid, carbon monoxide and polyclonal antibody against NADPH‐cytochrome P‐450 reductase from Jerusalem artichoke inhibit epoxide formation. Compared to freshly sliced tuber tissues, epoxidation activity was strongly enhanced in tissues aged in 20 mM aminopyrine solution. The possibility that 9, 10‐epoxidation of 9‐DDNA is catalyzed by the cytochrome P‐450 isoenzyme involved in lauric acid in‐chain hydroxylation in this plant was investigated.

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