Thiol-specific peroxidase that catalyzes the reduction of hydrogen peroxide and organic hydroperoxides to water and alcohols, respectively. Plays a role in cell protection against oxidative stress by detoxifying peroxides and as sensor of hydrogen peroxide-mediated signaling events (PubMed:2895105, PubMed:7961686, PubMed:10681558, PubMed:15210711, PubMed:19106090). Protects the cell against the oxidative stress caused by nascent-protein misfolding and aggregation (PubMed:24424024). Relays hydrogen peroxide as a signal to the transcription factor YAP1 by inducing the formation of intramolecular disulfide bonds in YAP1, which causes its nuclear accumulation and activation (PubMed:15706081, PubMed:19106090). Can act alternatively as peroxidase and molecular chaperone. Oxidative stress and heat shock exposure cause a reversible shift of the protein structure from low MW species to high MW complexes, triggering a peroxidase-to-chaperone functional switch. The chaperone function of the protein enhances resistance to heat shock (PubMed:15163410). [thioredoxin]-dithiol + a hydroperoxide = [thioredoxin]-disulfide + an alcohol + H2O Homodimer; disulfide-linked, upon oxidation (PubMed:8041739). Interacts with YAP1 via transient disulfide linkages (PubMed:19106090). Associates with ribosomes (PubMed:18271751). Colocalizes with sites of protein aggregation adjacent to active mitochondria (PubMed:24424024). 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. It can be reactivated by forming a transient disulfide bond with sulfiredoxin SRX1, which reduces the cysteine sulfinic acid in an ATP- and Mg-dependent manner. 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. Present with 378000 molecules/cell in log phase SD medium. Belongs to the peroxiredoxin family. AhpC/Prx1 subfamily.