title: Superoxide-dependent redox cycling of citrate-Fe3+: evidence for a superoxide dismutaselike activity.
abstract: Citrate-Fe3+, reportedly a physiological chelate, exhibits superoxide dismutaselike activity, as evidenced by the inhibition of xanthine oxidase-dependent cytochrome c reduction; the dismutation of xanthine oxidase-generated superoxide to hydrogen peroxide and oxygen, and the enhanced disproportionation of potassium superoxide. The catalytic activity of citrate-Fe3+ corresponds, on a molar basis, to 0.03% of that of copper- and zinc-containing superoxide dismutase. Although weak, this activity enables citrate-Fe3+ to inhibit superoxide and ADP-Fe3+ -dependent peroxidation of extracted microsomal lipids. Also, the dismutase activity of citrate-Fe3+ interferes with its ability to promote lipid peroxidation. It is proposed that chelation of Fe3+ by citrate may represent a protective mechanism against the deleterious consequences of superoxide generation.
mesh_terms: D002614:Chelating Agents; D002951:Citrates / Q000502:physiology*; D003574:Cytochrome c Group / Q000378:metabolism; D005290:Ferric Compounds / Q000502:physiology*; D006735:Horseradish Peroxidase / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D008054:Lipid Peroxides / Q000378:metabolism; D010084:Oxidation-Reduction; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
chemical_list: D002614:Chelating Agents; D002951:Citrates; D003574:Cytochrome c Group; D005290:Ferric Compounds; D008054:Lipid Peroxides; D013481:Superoxides; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase; D013482:Superoxide Dismutase