title: Studies on platelet lipoxygenase specificity towards icosapolyenoic and docosapolyenoic acids.
abstract: Two docosapolyenoic acids (22:5(n-3) and 22:5(n-6)) were isolated from the liver of normal and 18:3(n-3)-deficient trout, respectively. They were prepared by combined thin-layer chromatography (TLC) and reversed-phase high performance liquid chromatography (HPLC). Their purity, checked by capillary gas liquid chromatography, was greater than 95%. Each fatty acid was oxygenated into monohydroxy derivatives by human platelets. The hydroxy compounds were purified by TLC and HPLC and then derivatized for gas chromatography-mass spectrometry analysis. Whereas 22:5(n-6) was only converted into 14-OH-22:5, three hydroxy derivatives (11, 13 and 14) were obtained from 22:5(n-3). However, 13-hydroxy was not formed in the presence of aspirin, indicating that platelet lipoxygenase catalyses the formation of both 11- and 14-hydroxy derivatives from 22:5(n-3), as described previously, from 22:6(n-3). Further studies showed that 22:4(n-6) and 20:5(n-3) were only converted into 14- and 12-hydroxy derivatives. We conclude then that, besides the well-known n-9 oxygenation, lipoxygenase of human platelets is able to catalyse an n-12 oxygenation on docosapolyenoic acids of the n-3 family.
mesh_terms: D001792:Blood Platelets / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D005231:Fatty Acids, Unsaturated / Q000097:blood*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D007536:Isomerism; D008084:Lipoxygenase / Q000097:blood*; D010084:Oxidation-Reduction; D013379:Substrate Specificity
chemical_list: D005231:Fatty Acids, Unsaturated; D008084:Lipoxygenase