title: Bicarbonate enhances peroxidase activity of Cu,Zn-superoxide dismutase. Role of carbonate anion radical and scavenging of carbonate anion radical by metalloporphyrin antioxidant enzyme mimetics.
abstract: Much evidence exists for the increased peroxidase activity of copper, zinc superoxide dismutase (SOD1) in oxidant-induced diseases. In this study, we measured the peroxidase activity of SOD1 by monitoring the oxidation of dichlorodihydrofluorescein (DCFH) to dichlorofluorescein (DCF). Bicarbonate dramatically enhanced DCFH oxidation to DCF in a SOD1/H(2)O(2)/DCFH system. Peroxidase activity could be measured at a lower H(2)O(2) concentration ( approximately 1 microm). We propose that DCFH oxidation to DCF is a sensitive index for measuring the peroxidase activity of SOD1 and familial amyotrophic lateral sclerosis SOD1 mutants and that the carbonate radical anion (CO(3)) is responsible for oxidation of DCFH to DCF in the SOD1/H(2)O(2)/bicarbonate system. Bicarbonate enhanced H(2)O(2)-dependent oxidation of DCFH to DCF by spinal cord extracts of transgenic mice expressing SOD1(G93A). The SOD1/H(2)O(2)/HCO(3)(-)-dependent oxidation was mimicked by photolysis of an inorganic cobalt carbonato complex that generates CO(3). Metalloporphyrin antioxidants that are usually considered as SOD1 mimetic or peroxynitrite dismutase effectively scavenged the CO(3) radical. Implications of this reaction as a plausible protective mechanism in inflammatory cellular damage induced by peroxynitrite are discussed.
authors.affiliation: Biophysics Research Institute and Free Radical Research Center, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA.
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Joy
authors.initials: J
authors.lastname: Joseph
authors.forename: Mark
authors.initials: M
authors.lastname: Gurney
authors.forename: David
authors.initials: D
authors.lastname: Becker
authors.forename: B
authors.initials: B
authors.lastname: Kalyanaraman
mesh_terms: D024322:Amino Acids, Aromatic / Q000737:chemistry; D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics / Q000503:physiopathology; D000818:Animals; D052176:Azulenes; D001639:Bicarbonates / Q000737:chemistry / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D005452:Fluoresceins / Q000737:chemistry / Q000378:metabolism*; D016166:Free Radical Scavengers / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008665:Metalloporphyrins / Q000737:chemistry / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D015394:Molecular Structure; D018696:Neuroprotective Agents / Q000378:metabolism; D009589:Nitrogen Oxides / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism; D010084:Oxidation-Reduction; D009195:Peroxidase / Q000378:metabolism*; D012717:Sesquiterpenes / Q000378:metabolism; D019097:Spin Trapping; D013116:Spinal Cord / Q000201:enzymology / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*
chemical_list: D024322:Amino Acids, Aromatic; D052176:Azulenes; D001639:Bicarbonates; D005452:Fluoresceins; D016166:Free Radical Scavengers; D008665:Metalloporphyrins; D018696:Neuroprotective Agents; D009589:Nitrogen Oxides; D016877:Oxidants; D012717:Sesquiterpenes; C113630:azulenyl nitrone; D006861:Hydrogen Peroxide; D009195:Peroxidase; D013482:Superoxide Dismutase