Methemoglobin-hydrogen peroxide reaction

Other proteins such as methemoglobin and metmyoglobin have been observed to produce molecular oxygen in the presence of hydrogen peroxide, but at a very low rate (5). This may simply be a property of the heme, which can promote a low-level catalatic reaction in the absence of protein. Consequently, it is possible that all heme-containing proteins may exhibit catalatic reactions if assayed carefully, but such minor, largely nonquantifiable activities are not considered here. 

A different type of reaction is that between methemoglobin and hydrogen peroxide. Kobert (42) showed that a red-colored complex was formed and Keilin and Hartree (43) demonstrated that one peroxide molecule per iron atom was required. The complex which has absorption maxima at 585 m/u (a band) and 545 m/x (/ band) slowly decomposes, liberating methemoglobin, but is rapidly destroyed by hydrogen donors such as ascorbic acid and hydroquinone. Haurowitz (44) claimed that addition of alkali to the complex yielded alkaline methemoglobin and represented the reaction ... 

Whether lipid oxidation in muscle foods is catalysed by the iron redox cycle or by formation of the ferryl ions is not clear. However, ferrous ions react with lipid hydroperoxides much faster than with hydrogen peroxide. As shown above, if the reaction of metmyoglobin with hydroperoxides produces ferryl radicals capable of initiating lipid oxidation, it is necessary to prevent the formation of metmyoglobin or methemoglobin. At acidic pH, ferric myoglobin can initiate lipid oxidation in the presence of lipid hydroperoxides. 

Keilin, D., and Hartree, E. F. 1950. Reaction of methemoglobin with hydrogen peroxide. Nature 166, 513. 

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