Figure 1.

Catalytic cycle of peroxiredoxin (Prx) isoforms. (A) Typical 2-Cys Prxs (Prx1-4) first mediate the oxidation of C_P residues to sulfenic acid by H₂O₂, followed by the formation of an intermolecular disulfide bond with the C_R of another Prx subunit. Lastly, the oxidized Prx undergoes reduction by the thioredoxin (Trx)/Trx reductase (TrxR)/NADPH system. (B) Atypical 2-Cys Prx (Prx5) is similar to typical 2-Cys Prxs, except that they mediate the formation of an intramolecular disulfide bond with the C_R of the same Prx subunit. (C) 1-Cys Prx (Prx6) has only one conserved Cys residue so that they are recycled in sulfenic acid without forming a disulfide bond, which is reduced by glutathione (GSH) instead of Trx.