Lipid peroxidation during the oxidation of haemoproteins by hydroperoxides. Relation to electronically excited state...

The formation of electronically excited states during hydroperoxide metabolism is analysed in terms of recombination reactions involving secondary peroxyl radicals and scission of the O-O bond of peroxides by haemoproteins, mainly myoglobin. Both processes may be sequentially interrelated, for the cleavage of H2O2 by metmyoglobin leads to the formation of a strong oxidizing equivalent with the capability to promote peroxidation of polyunsaturated fatty acids. The decomposition of lipid hydroperoxides by ferryl-hydroxo complexes, as that formed during the oxidation of metmyoglobin by H2O2, is a source of peroxyl radicals, the recombination of which proceeds with elimination of a conjugated triplet carbonyl or singlet oxygen.