Reduces hydrogen peroxide and alkyl hydroperoxides with reducing equivalents provided through the thioredoxin or glutaredoxin system. May be involved in intracellular redox signaling. 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. [glutaredoxin]-dithiol + a hydroperoxide = [glutaredoxin]-disulfide + an alcohol + H2O Monomer. A number of isoforms are produced. According to EST sequences. Expressed in all tissues but mostly in reproductive tissues such as buds, flowers, siliques and seeds. Slightly induced by salt stress. 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 1-Cys peroxiredoxin, no C(R) is present and C(P) instead forms a disulfide with a cysteine from another protein or with a small thiol molecule. C(P) is reactivated by glutaredoxin (Grx). Belongs to the peroxiredoxin family. Prx5 subfamily.