Hemoglobin (Hb) is a potent pro-oxidant that accelerates lipid oxidation in fish muscles, leading to loss of sensory, functional, and nutritional quality. Phospholipase A2 (PLA2) is a lipolytic enzyme that catalyzes the liberation of a free fatty acid from the sn-2 position of phospholipids. We demonstrated that hydrolysis by PLA2 rendered lipid membranes of washed cod muscles resistant to trout Hb-mediated lipid oxidation, measured as lipid hydroperoxides (LHP) and thiobarbituric acid reactive substances (TBARS). Also, addition of PLA2 to washed cod muscle helped protect intact heme moiety of Hb from oxidative degradation. In addition, ferryl hemoglobin (ferryl-Hb), a hypervalent Hb species formed from the reaction between peroxides and Hb, was detected spectrophotometrically in the aqueous phase of trout Hb-containing washed cod following derivatization with sodium sulfide. In the presence of PLA2, the formation of ferryl-Hb was greatly suppressed. The presence of ferryl-Hb appears to be related to the sudden burst of methemoglobin (MHb) in the aqueous phase and lipid oxidation. Furthermore, compared with MHb, ferryl-Hb exhibited greater pro-oxidative activity when measured as TBARS but not when measured as LHP. These results demonstrate that PLA2 was able to inhibit lipid oxidation, delay ferryl-Hb and MHb formations and preserve intact heme in washed cod muscle.

Antioxidant effect of porcine pancreatic phospholipase A2 and detection and pro-oxidative activity of ferryl-hemoglobin in washed cod muscle

249th National Meeting (2015)

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