Effect of porcine pancreatic phospholipase A2 on lipid oxidation in muscle matrices

Author / Creator

Tatiyaborworntham, Nantawat, 1985-, author

Available as

Online

Physical

Summary

The objectives were to investigate the mechanisms by which phospholipase A2 (PLA2) inhibits hemoglobin (Hb)-mediated lipid oxidation in washed cod muscle (WCM) and to assess the effect of PLA2 on l...

The objectives were to investigate the mechanisms by which phospholipase A2 (PLA2) inhibits hemoglobin (Hb)-mediated lipid oxidation in washed cod muscle (WCM) and to assess the effect of PLA2 on lipid oxidation in minced muscles from cod, chicken, turkey, and pork. The effectiveness of PLA2 against Hb-mediated lipid oxidation depended on the concentration of PLA2, the availability of calcium ion, pH, and the stage of lipid oxidation. PLA2 inhibited lipid oxidation without preventing partitioning of hemin into the insoluble fraction of WCM consisting of myofibrillar proteins and lipid membranes. The ability of PLA2 and Hb to promote depletion of lipid hydroperoxides (LOOHs) was demonstrated in pre-oxidized WCM and pre-oxidized liposomes made from cod phospholipids. The depletion of LOOHs by PLA2 alone contributed to less formation of secondary products than when both PLA2 and Hb were present. Solid phase extraction (SPE) was used for fractionating and detecting hydroperoxy fatty acids released by PLA2 from LOOH-enriched liposomes. Both PLA2 and cysteine was required for partial depletion of LOOHs in the liposome model system. Sodium sulfide was used for the spectrophotometric detection of ferryl hemoglobin (ferryl Hb) which transiently formed during the onset of lipid oxidation in WCM treated with the ferrous trout Hb. The formations of methemoglobin and ferryl Hb were partially suppressed by PLA2. PLA2 inhibited lipid oxidation in minced muscles from cod and pork but promoted lipid oxidation in minced chicken and turkey. PLA2 remained pro-oxidative in trout Hb added-washed turkey breast muscle (WTM) at pH 6.2. Phospholipids and free fatty acids (FFAs) released from WCM and WTM treated with PLA2 were separated by SPE and characterized by gas chromatography. Eicosapentaenoic acid and docosahexaenoic acid appeared to be preferentially released from WCM by PLA2, while the primary hydrolysis products from WTM were saturated FFAs, oleic acid, linoleic acid and arachidonic acid.

Show More