Peroxiredoxins in antioxidant defense and redox regulation.

Peroxiredoxins constitute a family of peroxidases that lack prosthetic groups or catalytically active heteroatoms. Instead, their peroxidatic activity is due to a strictly conserved cysteine that is activated within a novel catalytic triad in which the cysteine thiol is coordinated to an arginine and a threonine or serine residue. Donor substrates are thiol compounds which differ between subtypes of peroxiredoxins and species. In pathogenic trypanosomatids that lack heme- or seleno-peroxidases peroxiredoxins have been shown to represent the major devices to detoxify hydroperoxides and an equivalent role may be assumed for other protozoal parasites and many bacterial pathogens. In mammals equipped with more efficient peroxidases the peroxiredoxins appear to be responsible for the redox regulation of diverse metabolic processes. The substantial differences in the cosubstrate requirements of the peroxiredoxins of pathogenic microorganisms and their mammalian host may be exploited to selectively inhibit the antioxidant defense of pathogens. Thereby, the pathogen would be more readily eliminated by the innate immune response of the host's phagocytes.