Double edge redox-implications for the interaction between endogenous thiols and copper ions: In vitro studies

Carrasco-Pozo, C; Aliaga, ME; Olea Azar C.; Speisky H.

Abstract

The present study investigated the redox-consequences of the interaction between various endogenous thiols (RSH)-glutathione, cysteine, homocysteine, γ-glutamyl-cysteine, and cysteinyl-glycine- and Cu 2+ ions, in terms of their free radical-scavenging, ascorbate-oxidizing and O 2 {radical dot} --generating properties of the resulting mixtures. Upon a brief incubation (3-30 min) with Cu 2+, the free radical-scavenging properties (towards ABTS {radical dot}+ and DPPH {radical dot}) and thiol-titrateable groups of the RSH added to the mixtures decreased significantly. Remarkably, both effects were only partial, even in the presence of a large molar Cu 2+-excess, and were unaffected despite increasing the incubation time. At equimolar concentrations, the RSH/Cu 2+ mixtures led to the formation of (EPR paramagnetic) Cu(II)-complexes that were time-stable and ascorbate-reducible, but redox-inactive towards oxygen. In turn, at a slight molar thiol-excess (3:1), the mixtures resulted in the formation of time-stable Cu(I)-complexes (EPR silent) that were unreactive towards ascorbate and oxygen. The only exception was seen for the thiol, glutathione, whose mixture with Cu 2+ mixture displayed a O 2 {radical dot} --generating capacity (cytochrome c- and lucigenin-reduction). The data indicate that, depending on their molar ratio, the interaction between Cu 2+ and the tested thiols would give place to mixtures containing either: (i) time-stable and ascorbate-reducible Cu(II)-complexes which display free radical-scavenging properties, or (ii) time-stable but redox-inactive towards oxygen Cu(I)-complexes. Among the latter, the only exception was that of glutathione. © 2008.

Más información

Título según WOS: Double edge redox-implications for the interaction between endogenous thiols and copper ions: In vitro studies
Título según SCOPUS: Double edge redox-implications for the interaction between endogenous thiols and copper ions: In vitro studies
Título de la Revista: BIOORGANIC & MEDICINAL CHEMISTRY
Volumen: 16
Número: 22
Editorial: PERGAMON-ELSEVIER SCIENCE LTD
Fecha de publicación: 2008
Página de inicio: 9795
Página final: 9803
Idioma: English
URL: http://linkinghub.elsevier.com/retrieve/pii/S0968089608009322
DOI:

10.1016/j.bmc.2008.09.068

Notas: ISI, SCOPUS