Hemoglobin auto-oxidation

Superoxide is formed (reaction 1) in the red blood cell by the auto-oxidation of hemoglobin to methemo-globin (approximately 3% of hemoglobin in human red blood cells has been calculated to auto-oxidize per day) in other tissues, it is formed by the action of enzymes such as cytochrome P450 reductase and xanthine oxidase. When stimulated by contact with bacteria, neutrophils exhibit a respiratory burst (see below) and produce superoxide in a reaction catalyzed by NADPH oxidase (reaction 2). Superoxide spontaneously dismu-tates to form H2O2 and O2 however, the rate of this same reaction is speeded up tremendously by the action of the enzyme superoxide dismutase (reaction 3). Hydrogen peroxide is subject to a number of fates. The enzyme catalase, present in many types of cells, converts... 

Adverse events rates differ and seem to depend on the extent of polymerization of the product pi "]. HBOC-201 is a purified cell-free glutaraldehyde cross-linked and polymerized bovine hemoglobin that is susceptible to auto-oxidation to methemoglobin the plasma methemoglobin concentration increases dose-dependently l i%... 

The hemoglobin of cats is highly sensitive to auto-oxidation and Heinz body formation. This sensitivity is probably caused by different amino acid paUems or differences in the sulfliydiyl content of the hemoglobin. 

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