Oxylipin metabolism in the red alga Gracilariopsis lemaneiformis: mechanism of formation of vicinal dihydroxy fatty acids.
Conversion of arachidonic acid into the vicinal diol fatty acid 12R,13S-dihydroxy-5Z,8Z,10E,14Z-eicosatetraenoic acid using an acetone powder of the marine red alga, Gracilariopsis lemaneiformis, occurred via intermediate formation of 12S-hydroperoxy-5Z,8Z,10E,14Z-eicosatetraenoic acid. Incubations of the linoleic acid-derived 13S- and 13R-hydroperoxy-9Z,11E-octadecadienoic acids led to the formation of 13R,14S-dihydroxy-9Z,11E-octadecadienoic acid and 13S,14S-dihydroxy-9Z,11E-octadecadienoic acid, respectively, whereas incubation of 9S-hydroperoxy-10E,12Z-octadecadienoic acid resulted in the formation of 8S,9R-dihydroxy-10E,12Z-octadecadienoic acid. Experiments with 18O2-labeled 13S-hydroperoxyoctadecadienoic acid demonstrated that the oxygens of the two hydroxyl groups of 13R,14S-dihydroxy-9Z,11E-octadecadienoic acid originated in the hydroperoxy group of the substrate. Furthermore, experiments with mixtures of unlabeled and 18O2-labeled 13S-hydroperoxyoctadecadienoic acid showed that conversion into 13R,14S-dihydroxyoctadecadienoic acid occurred by a reaction involving an intramolecular hydroxylation at C-14 by the distal hydroperoxide oxygen. The existence of a hydroperoxide isomerase in G. lemaneiformis which catalyzes the conversion of fatty acid hydroperoxides into vicinal diol fatty acids is postulated.
Department of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden.
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Gerwick
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Moghaddam
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Hamberg
D001095:Arachidonic Acids / Q000737:chemistry / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis* / Q000737:chemistry; D006900:Hydroxylation; D019746:Intramolecular Oxidoreductases; D007535:Isomerases / Q000378:metabolism; D015289:Leukotrienes / Q000737:chemistry / Q000378:metabolism; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000737:chemistry / Q000378:metabolism; D000461:Rhodophyta / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*
D001095:Arachidonic Acids; D005227:Fatty Acids; D015289:Leukotrienes; D008041:Linoleic Acids; C021201:12-HPETE; D019787:Linoleic Acid; D007535:Isomerases; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase