Formation of perthiyl free radicals in irradiated glutathione

The irradiation of reduced (GSH) or oxidized (GSSG) glutathione in the solid state was performed using gamma-rays from Co-60 or high-energy electrons from an accelerator. In GSSG, perthiyl radicals (GSS') were created in addition to carbon-centred radicals as seen by electron paramagnetic resonance spectroscopy. The quantity was independent of the dose rate (electrons or gamma-rays) and of the presence of oxygen. In GSH, perthiyl radicals were also created, although in a smaller quantity. Among end-products in irradiated GSSG, we find GSH. Thus, sulphur functions are reduced by irradiation in the solid state

Detoxification of superoxide without production of H(2)O(2): Antioxidant activity of superoxide reductase complexed with ferrocyanide

The superoxide radical O(2)(·̅) is a toxic by-product of oxygen metabolism. Two O(2)(·̅) detoxifying enzymes have been described so far, superoxide dismutase and superoxide reductase (SOR), both forming H(2)O(2) as a reaction product. Recently, the SOR active site, a ferrous iron in a [Fe(2+) (N-His)(4) (S-Cys)] pentacoordination, was shown to have the ability to form a complex with the organometallic compound ferrocyanide. Here, we have investigated in detail the reactivity of the SOR–ferrocyanide complex with O(2)(·̅) by pulse and γ-ray radiolysis, infrared, and UV-visible spectroscopies. The complex reacts very efficiently with O(2)(·̅). However, the presence of the ferrocyanide adduct markedly modifies the reaction mechanism of SOR, with the formation of transient intermediates different from those observed for SOR alone. A one-electron redox chemistry appears to be carried out by the ferrocyanide moiety of the complex, whereas the SOR iron site remains in the reduced state. Surprisingly, the toxic H(2)O(2) species is no longer the reaction product. Accordingly, in vivoexperiments showed that formation of the SOR–ferrocyanide complex increased the antioxidant capabilities of SOR expressed in an Escherichia coli sodA sodB recA mutant strain. Altogether, these data describe an unprecedented O(2)(·̅) detoxification activity, catalyzed by the SOR–ferrocyanide complex, which does not conduct to the production of the toxic H(2)O(2) species