This study investigates the potential basis for enhancement of oxymyoglobin (OxyMb) oxidation by lipid oxidation products. Aldehydes known to be formed as secondary lipid oxidation products were combined with OxyMb in aqueous solution at 37 degrees C and pH 7.4. Metmyoglobin (MetMb) formation was greater in the presence of alpha,beta-unsaturated aldehydes than their saturated counterparts of equivalent carbon chain length. Additionally, increasing chain length from hexenal through nonenal resulted in increased MetMb formation (P < 0.05). Electrospray ionization mass spectrometry (ESI-MS) revealed that OxyMb incubated with 4-hydroxynonenal (HNE) at pH 7.4 at 37 degrees C yielded myoglobin molecules adducted with one to three molecules of HNE from 0.5 to 2 h of incubation, respectively. A prooxidant effect of HNE was noted at pH 7.4 but was not apparent at pH 5.6 when compared to the control (P < 0.05). This appeared to be due to rapid OxyMb autoxidation at this pH compared to pH 7.4. ESI-MS demonstrated that adduction of HNE to OxyMb occurred at pH 5.6. This research demonstrates that alpha, beta-unsaturated aldehydes accelerate OxyMb oxidation and appear to do so via covalent attachment.

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