title: Redox-changes associated with the glutathione-dependent ability of the Cu(II)-GSSG complex to generate superoxide.
abstract: The intracellularly-occurring Cu(I)-glutathione complex (Cu(I)-[GSH](2)) has the ability to reduce molecular oxygen into superoxide. Removal of such radicals leads to the irreversible conversion of Cu(I)-[GSH](2) into the redox-inactive Cu(II)-GSSG complex. The present study addressed the potential of reduced glutathione, ascorbate and superoxide to reductively regenerate Cu(I)-[GSH](2) from Cu(II)-GSSG, and investigated the redox changes involved in such process. Results show that: (i) among the three tested reductants, only GSH is able to reduce the Cu(II) bound to GSSG; (ii) during the reduction of Cu(II)-GSSG, a Cu(I)-GSSG intermediate would be formed (supported here by Cu(I) and GSSG recovery data and by NMR studies); (iii) when GSH is present in a molar excess equal or greater than 1:3, the reduction of Cu(II)-GSSG into Cu(I)-[GSH](2) is quantitative and complete. Under such conditions, the Cu(II)-GSSG complex acquires a superoxide-generating capacity which is identical to that seen with the Cu(I)-[GSH](2) complex. Within cells, the concentrations of GSH are at least 2- to 3-fold order of magnitude higher than those expected for the Cu(II)-GSSG complex. Thus, we postulate that the interaction between GSH and Cu(II)-GSSG could be seen as a potential mechanism to regenerate continuously the Cu(I)-[GSH](2) complex and thereby affect the ability of the latter to generate superoxide.
authors.affiliation: Facultad de Química, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago 6094411, Chile. mealiaga@uc.cl
authors.forename: Margarita E
authors.initials: ME
authors.lastname: Aliaga
authors.forename: Camilo
authors.initials: C
authors.lastname: López-Alarcón
authors.forename: Luis
authors.initials: L
authors.lastname: García-Río
authors.forename: Manuel
authors.initials: M
authors.lastname: Martín-Pastor
authors.forename: Hernán
authors.initials: H
authors.lastname: Speisky
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D005978:Glutathione / Q000737:chemistry* / Q000378:metabolism; D019803:Glutathione Disulfide / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D013481:Superoxides / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D013481:Superoxides; D003300:Copper; D005978:Glutathione; D019803:Glutathione Disulfide