Products of Metmyoglobin Oxidation at Acid pH

Abstract

When the oxidation of metmyoglobin or methaemoglobin by H 20 2 is carried out at pH 5 or less the principal product absorbs at 525 m!'-. It is taken to be the conjugate acid of the ferrylmyoglobin or ferrylhaemoglobin which is the main oxidation product at neutral pH and which absorbs at 545 m!'-. It appears to be susceptible to further attack by H202, yielding an inert ferric complex which absorbs at 586 m!'-, and which cannot be reduced to an oxygen carrier. Formation of the 586 m!,- complex could be a minor factor in the aging of erythrocytes. Whale metmyoglobin differs from that of horse in not being oxidized to the ferryl state by chloroiridate ion if the pH is less than 6·5.