title: Superoxide-dependent and ascorbate-dependent formation of hydroxyl radicals in the presence of copper salts: a physiologically significant reaction?
abstract: Copper (Cu2+) ions at physiological concentrations can promote the formation of hydroxyl radical (OH) or a species of equivalent reactivity. The reaction requires H2O2 and a reducing agent. Reduction of Cu2+ can be achieved by superoxide ion generated by a mixture of hypoxanthine and xanthine oxidase or added directly as its potassium salt. Reduction of Cu2+ can also be achieved by ascorbic acid. Hence both O2- -dependent and ascorbate-dependent formation of OH from H2O2 in the presence of Cu2+ can be observed. Only the former reaction is significantly inhibited by superoxide dismutase. The binding of Cu2+ to histidine or albumin at physiological concentrations decreases the formation of OH radicals in free solution in the presence of either ascorbate or an (O2- -generating system. It is suggested that OH is still formed but reacts immediately with the binding molecule.
mesh_terms: D001205:Ascorbic Acid; D055598:Chemical Phenomena; D002621:Chemistry; D003300:Copper; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005609:Free Radicals; D006861:Hydrogen Peroxide; D006878:Hydroxides; D017665:Hydroxyl Radical; D010100:Oxygen; D011485:Protein Binding; D013481:Superoxides
chemical_list: D004791:Enzyme Inhibitors; D005609:Free Radicals; D006878:Hydroxides; D013481:Superoxides; D017665:Hydroxyl Radical; D003300:Copper; D006861:Hydrogen Peroxide; D001205:Ascorbic Acid; D010100:Oxygen