Sequence of heme decomposition by the coupled oxidation of myoglobin with ascorbic acid.

Occurrence of a biliverdin-iron complex or verdoheme as the final oxidation product of heme moiety in the coupled oxidation of myoglobin and ascorbic acid in air was evidenced and the sequence of heme decomposition in this reaction system was concluded to proceed in the order of protoheme, hydroxyheme and biliverdin-iron complex or verdoheme. The final oxidation product usually remains attaached to globin and appears to give a diffuse absorption possibly with a peak at 760 nm at neutral pH. In alkaline solution the compound exhibits an absorption peak at 840 nm, and when reduced with Na(2)S(2)O(4), it is readily converted to biliverdin which exhibits a large absorption with a peak originally at 800 nm, being followed by a gradual shift to 760 nm.