ω10-Lipoxygenase products of α-linolenic acid are esterified to phospholipids inHydra vulgaris

Abstract

We have recently reported the occurrence of 9(R)-hydroxy-, 9(R)-hydroperoxy- and 9-keto-octadeca-10E,12Z,15Z-trienoic acids (9-HOTrE, 9-HPOTrE and 9-KOTrE) inHydra vulgaris, and their biosynthesis from α-linolenic acid (α-LA) through the action of an enantioselective ω 10(R)-lipoxygenase (ω10-LO). Here we describe the finding of these α-LA metabolites as esters to the 2-position of phosphatidylcholine, phosphatidylethanolamine and, in trace amounts, phosphatidylinositol. Small amounts of a compound co-eluting with an authentic standard of 9(R)-hydroxy-octadeca-10E,12Z-dienoic acid, a metabolite potentially derived from the action of ω 10-LO on linoleic acid, were also found esterified with phospholipids. Since direct peroxidation of membrane lipids has been described, experiments were aimed at establishing whether α-LA metabolite-containing phospholipids could originate, inH. vulgaris, from either spontaneous or ω 10-LO-catalyzed oxidation of phospholipid-bound α-LA. Incubation of either unlabelled or radiolabelled PUFA-containing phosphoglycerides withH. vulgaris ω 10-LO did not result in their peroxidation. This suggests that α-LA and LA metabolites are incorporated into glycerophospholipids after their formation by ω 10-LO, and that, as in mamals, membrane phospholipids may serve as a reservoir for these bioactive compounds. This is the first example in an invertebrate species of lipoxygenase products esterified to phosphoglycerides.