Figure 2.

Peroxiredoxin activity. The reduced Cys52 in Prx2 (C_PSH) is oxidized by H₂O₂ and other oxidants to sulfenic acid (C_P-SOH). This C_PSOH reacts with the C_RSH, forming an intermolecular disulfide bridge. The disulfide-oxidized Prx2 is predominantly a dimer and is reduced by Trx, TR, and NADPH. The oxidized C_PSOH can alternatively react with a second oxidant molecule to yield the hyperoxidized sulfinic acid (C_PSO₂). The latter can either be repaired to the active enzyme by sulfiredoxin (Srx) or form stacked decamer high molecular weight structures. The structure of decameric Prx2 (5IJT) shows reactive cysteine residues in yellow, and each dimer is shown in green and blue, as sides of the pentagon.