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. May represent an important antioxidant defense against cytotoxic peroxides, especially peroxynitrite, which can be formed by activated macrophages during infection. [mycoredoxin]-L-dithiol + a hydroperoxide = [mycoredoxin]-L-disulfide + an alcohol + H2O Homodimer. Forms both dimers and octamers; a tightly-associated dimer and a ring-like octamer. 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) can be reactivated through a mixed disulfide with the N-terminal cysteine of mycoredoxin-1 (Mrx1), resolved by its C-terminal cysteine, or by a mixed disulfide with mycothiol, resolved by a second molecule of mycothiol or by mycoredoxin-1. Belongs to the peroxiredoxin family. AhpE subfamily.