Lipoxygenase in trout gill tissue acting on arachidonic, eicosapentaenoic and docosahexaenoic acids

Lipoxygenase activity was characterized in the gill tissue of fresh-water trout. Incubation of arachidonic acid with gill preparations yielded 12-hydroxyeicosatetraenoic acid as the major product, suggesting a 12-lipoxygenase. Eicosapentaenoic acid was similarly converted to the 12-hydroxyeicosapentaenoic acid. Both arachidonic acid and docosahexaenoic acid were converted with equal apparent velocities and affinities into single monohydroxy derivatives. Analyses of the hydroxy product of docosahexaenoic acid were consistent with 14-hydroxydocosahexaenoic acid. This enzyme activity was localized to the cytosolic fraction and displayed a broad pH optimum around pH 7. The enzyme was insensitive to the cyclooxygenase inhibitors indomethacin and aspirin but activity was strongly inhibited in the presence of the lipoxygenase inhibitors, SnCl₂ (5 mM), esculetin (10 μM) and eicosatetraynoic acid (100 μM).