The biosynthesis of jasmonic acid: a physiological role for plant lipoxygenase.

Linolenic acid was converted to a cyclic product, 12-oxo-phytodienoic acid, by lipoxygenase and hydroperoxide cyclase enzymes present in Vicia faba pericarp. Isotope labeling studies in which [U-14C] 12-[180] oxo-phytodienoic acid was incubated with thin sections of pericarp tissue showed that 12-oxo-phytodienoic acid is a biosynthetic precursor to jasmonic acid, a plant growth regulator which promotes senescence. Key enzymes proposed for this pathway are a reductase enzyme which reduces a double bond in the cyclopentenone ring, and beta-oxidation enzymes which remove six carbons from the carboxyl end of the molecule.