Lipoxygenase-Catalyzed Oxidation of N-6 and N-3 Polyunsaturated Fatty Acids: Relevance to and Activity in Fish Tissue

Lipid peroxidation is an important process responsible for the flavor deterioration of many plant and animal foods. In order to understand possible mechanisms of initiation, a soybean lipoxygenase-polyunsaturated fatty acid model system was studied. The rate of enzyme-initiated oxidation was monitored by both oxygen consumption and diene conjugation. The hydroperoxides from an n-6 fatty acid, i.e. arachidonic, and n-3 fatty acids, i.e. linolenic, eicosapentaenoic, and docosahexaenoic acids were reduced and analyzed by reverse-phase high pressure liquid chromatography and gas chromatography/mass spectrometry. The lipoxygenase specifically catalyzed oxygenation at the n-6 carbon of both n-3 and n-6 fatty acids. Lipoxygenase activity was demonstrated in skin homogenate from rainbow trout and its role in off-flavor development is discussed.