Oxodiene formation during the Vicia sativa lipoxygenase-cataylzed reaction: occurrence of dioxygenase and fatty acid lyase activities associated in a single protein

An enzyme with at least dual activities, lipoxygenase and fatty acid lyase, has been isolated from Vicia sativa seeds. The enzyme utilizes directly linoleic acid as substrate. The enzyme had a pH optimum at 5.8 for the two activities and converted linoleic acid into two products : 9-hydroperoxylinoleic acid and trans-2, cis-4 decadienal. The enzyme does not act on 13- or 9-fatty acid hydroperoxide isomers. An enzymatic reaction for the biogenesis of trans-2, cis-4-decadienal is proposed. This involves the synthesis of an intermediate peroxyl radical due to oxygen insertion in carbon 9 of linoleic acid. This intermediate peroxyl radical may be converted into 9-HPOD and 2,4-decadienal