InterPro domain: IPR000866

Peroxiredoxins (Prxs) are a ubiquitous family of antioxidant enzymes that also control cytokine-induced peroxide levels which mediate signal transduction in mammalian cells. Prxs can be regulated by changes to phosphorylation, redox and possibly oligomerisation states. Prxs are divided into three classes: typical 2-Cys Prxs; atypical 2-Cys Prxs; and 1-Cys Prxs. All Prxs share the same basic catalytic mechanism, in which an active-site cysteine (the peroxidatic cysteine) is oxidised to a sulphenic acid by the peroxide substrate. The recycling of the sulphenic acid back to a thiol is what distinguishes the three enzyme classes. Using crystal structures, a detailed catalytic cycle has been derived for typical 2-Cys Prxs, including a model for the redox-regulated oligomeric state proposed to control enzyme activity [ 1 ].

Alkyl hydroperoxide reductase (Ahp) has two subunits, the small AhpC subunit and the large AhpF subunit [ 2 ]. AhpC is responsible for directly reducing organic hydroperoxides in its reduced dithiol form. Thiol specific antioxidant (TSA) is a physiologically important antioxidant which constitutes an enzymatic defence against sulphur-containing radicals and protects the cell against the oxidative stress caused by protein misfolding and aggregation [ 3 ]. This entry contains AhpC and TSA, as well as related proteins.

1. Structure, mechanism and regulation of peroxiredoxins. Trends Biochem. Sci. 28, 32-40
2. Alkyl hydroperoxide reductase is important for oxidative stress resistance and symbiosis in Azorhizobium caulinodans. FEMS Microbiol. Lett. 366, 1327-35
3. The yeast peroxiredoxin Tsa1 protects against protein-aggregate-induced oxidative stress. J. Cell. Sci. 127