Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively (PubMed:15099742). In I2 pharyngeal neurons, required for the inhibition of feeding in response to light and hydrogen peroxide (PubMed:25640076). In the intestine, plays a role in protecting cells against oxidative stress by detoxifying peroxides such as hydrogen peroxide (PubMed:15099742, PubMed:19064914, PubMed:20649472). In addition, plays a role in the recovery from oxidative stress induced by hydrogen peroxide (PubMed:20649472). In its hyperoxidized form (induced by hydrogen peroxide), confers protection against heat stress (PubMed:19064914). However, has a low tendency for overoxidation during the normal lifespan (PubMed:20964547). Increases sensitivity to cytotoxity caused by metalloids and heavy metals such as arsenic and cadmium by playing a role in inhibiting the expression of phase II detoxification genes such as gcs-1 in intestinal cells (PubMed:19064914, PubMed:25204677). In addition, in response to arsenite, promotes the secretion of the insulin ligand daf-28 into the pseudocoelom, which negatively regulates the activities of daf-16 and skn-1 (PubMed:25808059). Plays a role in promoting longevity (PubMed:19064914, PubMed:24889636). Plays a role in the mitohormetic pathway by promoting the activation of pmk-1 in response to the drug metformin (PubMed:24889636). [thioredoxin]-dithiol + a hydroperoxide = [thioredoxin]-disulfide + an alcohol + H2O Activated following oxidation of the conserved redox-active cysteine residue, which subsequently allows for the oxidation and activation of substrates. Monomer and homodimer; disulfide-linked (PubMed:19064914). Under nonstress conditions, present in the reduced monomeric form (PubMed:19064914). Forms active hyperoxidized monomers and disulfide-linked homodimers upon oxidation by hydrogen peroxide (PubMed:19064914). Forms active oxidized homodimers in response to the drug metformin (PubMed:24889636). Expressed in the gonad, neurons and intestine (at protein level) (PubMed:19064914). Expressed in the pharyngeal inter-neuron I4 and the sensory interneuron I2 (PubMed:15099742, PubMed:25640076). Expressed in the intestine, pharyngeal muscle 1, vulval muscle, body wall muscle, epithelial cells e1 and e3, and neurons in the head and tail (PubMed:25640076). Expressed throughout embryonic, larval and adult stages (PubMed:15099742, PubMed:19064914). Highly expressed at the L3 larval stage at 25 degrees Celsius (PubMed:29055282). Up-regulated in response to the drug metformin. The enzyme can be inactivated by further oxidation of the cysteine sulfenic acid (C(P)-SOH) to sulphinic acid (C(P)-SO2H) instead of its condensation to a disulfide bond. Reduced size, egg production and brood size (PubMed:15099742). Survival in response to heat and oxidative stress induced by peroxides is comparable to wild-type (PubMed:15099742). RNAi-mediated knockdown increases lifespan in response to the heavy metal arsenite (PubMed:25808059). RNAi-mediated knockdown increases expression of gcs-1 and further increases gcs-1 expression in response to the heavy metal arsenite (PubMed:19064914). RNAi-mediated knockdown increases the expression of isoform a of skn-1 in intestinal nuclei (PubMed:25808059). The active site is a conserved redox-active cysteine residue, the peroxidatic cysteine (C(P)), which makes the nucleophilic attack on the peroxide substrate. The peroxide oxidizes the C(P)-SH to cysteine sulfenic acid (C(P)-SOH), which then reacts with another cysteine residue, the resolving cysteine (C(R)), to form a disulfide bridge. The disulfide is subsequently reduced by an appropriate electron donor to complete the catalytic cycle. In this typical 2-Cys peroxiredoxin, C(R) is provided by the other dimeric subunit to form an intersubunit disulfide. The disulfide is subsequently reduced by thioredoxin. Belongs to the peroxiredoxin family. AhpC/Prx1 subfamily.