How relevant is the reoxidation of ferrocytochrome c by hydrogen peroxide when determining superoxide anion production?
In a recent publication [(1987) FEBS Lett. 210, 195-198] the authors claim the use of cytochrome c to detect superoxide anion underestimates the real rate of superoxide anion formation on the basis that: (i) the rate of uric acid formation by xanthine oxidase is about 4-fold faster than the rate of cytochrome c reduction and (ii) hydrogen peroxide formed upon dismutation of the superoxide anion generated by xanthine oxidase is capable of reoxidizing ferrocytochrome c. That paper may have been misleading for readers not very familiar with the field of oxygen radicals, since both assumptions are, in fact, incorrect. In this report we demonstrate that the build up in concentration of H2O2 during most reactions in which superoxide anion is being produced is not enough to affect the rate of cytochrome c reduction. Our results suggest that the authors may have been misled by an artifact due to exposure of the samples containing H2O2 to UV light, which generates hydroxyl radicals by photolysis.
Turrens
J F
JF
Department of Biochemistry, College of Medicine, University of South Alabama, Mobile 36688.
McCord
J M
JM
D000838:Anions; D002850:Chromatography, Gel; D003574:Cytochrome c Group / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000528:radiation effects; D006878:Hydroxides / Q000378:metabolism; D017665:Hydroxyl Radical; D007700:Kinetics; D010084:Oxidation-Reduction; D010782:Photolysis; D013481:Superoxides / Q000378:metabolism*; D014466:Ultraviolet Rays; D014527:Uric Acid / Q000378:metabolism; D014969:Xanthine Oxidase / Q000378:metabolism
D000838:Anions; D003574:Cytochrome c Group; D006878:Hydroxides; D013481:Superoxides; D014527:Uric Acid; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D014969:Xanthine Oxidase