title: Characterization of a C-5,13-Cleaving Enzyme of 13(S)-Hydroperoxide of Linolenic Acid by Soybean Seed.
abstract: An activity was found in mature soybean seeds (Glycine max L. cv Century) that cleaved 13(S)-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid (13S-HPOT) into 13-oxo-9(Z),11(E)-tridecadienoic acid and two isomeric pentenols, 2(Z)-penten-1-ol and 1-penten-3-ol. Isomeric pentene dimers were also produced and were presumably derived from the combination of two pentene radicals. 13(S)-Hydroperoxy-9(Z),11(E)-octadecadienoic acid (13S-HPOD) was, by contrast, a poor substrate. Activity with 13S-HPOT increased 24-fold under anaerobic conditions reminiscent of a similar anaerobic promoted reaction of 13S-HPOD catalyzed by lipoxygenase (LOX) in the presence of linoleic acid. However, prior to ion-exchange chromatography, cleavage activity did not require linoleic acid. After separation by gel filtration followed by ion-exchange chromatography, cleavage activity was lost but reappeared in the presence of either linoleic acid or dithiothreitol. Under these conditions cleavage activity was coincident with the activity of types 1 and 2 LOX. LOX inhibitors suppressed the cleavage reaction in a manner similar to inhibition of LOX activity. Heat-generated alkoxyl radicals derived from either 13S-HPOT or 13S-HPOD afforded similar products and yields of 13-oxo-9(Z),11(E)-tridecadienoic acid compared to the enzymic reaction. The product 1-penten-3-ol may be the precursor of the "raw-bean" volatile ethylvinylketone.
authors.affiliation: United States Department of Agriculture/Agricultural Research Service/National Center for Agricultural Utilization Research, Phytoproducts Research Unit, Peoria, Illinois 61604 (Y.P.S., M.J.G., H.W.G.).
authors.forename: Y. P.
authors.initials: YP
authors.lastname: Salch
authors.forename: M. J.
authors.initials: MJ
authors.lastname: Grove
authors.forename: H.
authors.initials: H
authors.lastname: Takamura
authors.forename: H. W.
authors.initials: HW
authors.lastname: Gardner