Lipid oxidation–induced oxidation in emu and ostrich myoglobins

Emu and ostrich are ratites gaining increasing popularity as sources of low-fat meats. Secondary products of lipid oxidation, such as 4-hydroxy-2-nonenal (HNE), compromise myoglobin redox stability in a species-specific manner. However, the molecular basis of lipid oxidation–induced oxidation in ratite myoglobins has not been investigated. Therefore, our objective was to characterize lipid oxidation–induced oxidation in ratite myoglobins, in comparison with beef myoglobin. At physiological condition (pH 7.4, 37 °C) HNE accelerated (P < 0.05) oxidation of emu, ostrich, and beef oxymyoglobins. Autoxidation and HNE-induced oxidation were greater (P < 0.05) in ostrich oxymyoglobin than in emu and beef oxymyoglobins. Mass spectrometric analyses revealed that HNE formed mono-adduct with both emu and ostrich myoglobins after 6 h of incubation. Tandem mass spectrometry demonstrated that HNE adducted histidine 36 in ostrich myoglobin, whereas histidines 34 and 36 were adducted in emu myoglobin. The results indicate that primary structure of ratite myoglobins influences their redox stability in the presence of prooxidants.