How superoxide radical damages the cell.

Superoxide is considered to be poorly reactive, and cell damage has been attributed to HO. generated via the Haber-Weiss reaction. The function of O2- in this reaction is only to reduce Fe3+ to Fe2+. In vivo, however, superoxide could not out-compete cellular reductants such as glutathione, NADPH, and ascorbate, which makes the observed O2- toxicity rather puzzling. Little attention has been paid to the idea that, irrespective of its poor chemical reactivity, superoxide might be capable of interacting directly with specific intracellular targets; and that even the Haber-Weiss reaction might be a consequence of such direct interactions. This paper summarizes latest data that support the concept of such a mechanism.