title: Kinetics of the oxidation of reduced Cu,Zn-superoxide dismutase by peroxymonocarbonate.
abstract: Kinetic evidence is reported for the role of the peroxymonocarbonate, HOOCO(2)(-), as an oxidant for reduced Cu,Zn-superoxide dismutase-Cu(I) (SOD1) during the peroxidase activity of the enzyme. The formation of this reactive oxygen species results from the equilibrium between hydrogen peroxide and bicarbonate. Recently, peroxymonocarbonate has been proposed to be a key substrate for reduced SOD1 and has been shown to oxidize SOD1-Cu(I) to SOD1-Cu(II) much faster than H(2)O(2). We have reinvestigated the kinetics of the reaction between SOD1-Cu(I) and HOOCO(2)(-) by using conventional stopped-flow spectrophotometry and obtained a second-order rate constant of k=1600±100M(-1)s(-1) for SOD1-Cu(I) oxidation by HOOCO(2)(-). Our results demonstrate that peroxymonocarbonate oxidizes SOD1-Cu(I) to SOD1-Cu(II) and is in turn reduced to the carbonate anion radical. It is proposed that the dissociation of His61 from the active site Cu(I) in SOD-Cu(I) contributes to this chemistry by facilitating the binding of larger anions, such as peroxymonocarbonate.
authors.affiliation: Laboratory of Pharmacology and Toxicology, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Kalina
authors.initials: K
authors.lastname: Ranguelova
authors.forename: Douglas
authors.initials: D
authors.lastname: Ganini
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: Bonini
authors.forename: Robert E
authors.initials: RE
authors.lastname: London
authors.forename: Ronald P
authors.initials: RP
authors.lastname: Mason
mesh_terms: D000818:Animals; D002254:Carbonates / Q000737:chemistry*; D020134:Catalytic Domain; D002417:Cattle; D007700:Kinetics; D008958:Models, Molecular; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000737:chemistry; D013482:Superoxide Dismutase / Q000737:chemistry*; D000072105:Superoxide Dismutase-1
chemical_list: D002254:Carbonates; D016877:Oxidants; D017382:Reactive Oxygen Species; C512862:peroxycarbonic acid; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1