Iron release from metmyoglobin, methaemoglobin and cytochrome c by a system generating hydrogen peroxide.

The reaction of H2O2 with resting metmyoglobin (MetMb), methaemoglobin (MetHb) and cytochrome-c (Cyt-c) was studied in the Soret and visible regions. The differences between the original and the final peak heights of the native haemproteins at 408 nm was found to be directly proportional to the loss of iron from the molecule. The release of iron from haemproteins was studied in a system generating H2O2 continuously at a low rate by an enzymic system, or by addition of large amounts of H2O2. Cytochrome-c, methaemoglobin and metmyoglobin during interaction with H2O2 at a concentration of 200 microM release 40%, 20% and 3%, respectively, of molecular iron after 10 min. The inhibition of haem degradation and iron release by enzymatically-generated H2O2 was determined using several hydroxyl radical scavengers, reducing agents and antioxienzymes, such as superoxide dismutase, catalase and caeruloplasmin.