The influence of porphyrins on iron-catalysed generation of hydroxyl radicals.
Uroporphyrin I, haematoporphyrin and haematoporphyrin derivative had no effect on O2-. generation during oxidation of hypoxanthine by xanthine oxidase and on the formation of hydroxyl radicals (OH.) in the hypoxanthine/xanthine oxidase/Fe3+-EDTA/deoxyribose system. On the other hand, these porphyrins strongly inhibited O2-. formation in a horseradish peroxidase/H2O2/NADPH mixture, whereas they augmented OH. generation in this system after addition of Fe3+-EDTA. Experimental evidence suggests that these observations should be ascribed to the formation of a porphyrin anion radical in the horseradish peroxidase/NADPH system. The formation of this anion radical was confirmed by e.s.r. spectroscopy. This radical is apparently unable to reduce cytochrome c, but it can replace O2-. in the OH.-generating Haber-Weiss reaction.
Van Steveninck
J
J
Sylvius Laboratories, Department of Medical Biochemistry, Leiden, The Netherlands.
Boegheim
J P
JP
Dubbelman
T M
TM
Van der Zee
J
J
D002384:Catalysis; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D017324:Hematoporphyrin Derivative; D006415:Hematoporphyrins / Q000494:pharmacology; D006735:Horseradish Peroxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D006878:Hydroxides / Q000378:metabolism*; D017665:Hydroxyl Radical; D019271:Hypoxanthine; D007042:Hypoxanthines / Q000378:metabolism; D007501:Iron / Q000494:pharmacology*; D009249:NADP / Q000378:metabolism; D011166:Porphyrins / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000378:metabolism
D005609:Free Radicals; D006415:Hematoporphyrins; D006878:Hydroxides; D007042:Hypoxanthines; D011166:Porphyrins; D019271:Hypoxanthine; D017665:Hydroxyl Radical; D009249:NADP; D017324:Hematoporphyrin Derivative; D006861:Hydrogen Peroxide; D007501:Iron; D006735:Horseradish Peroxidase; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase