Peroxiredoxin (PRX) family, Atypical 2-cys PRX subfamily; composed of PRXs containing peroxidatic and resolving cysteines, similar to the homodimeric thiol specific antioxidant (TSA) protein also known as TRX-dependent thiol peroxidase (Tpx). Tpx is a bacterial periplasmic peroxidase which differs from other PRXs in that it shows substrate specificity toward alkyl hydroperoxides over hydrogen peroxide. As with all other PRXs, the peroxidatic cysteine (N-terminal) of Tpx is oxidized into a sulfenic acid intermediate upon reaction with peroxides. Tpx is able to resolve this intermediate by forming an intramolecular disulfide bond with a conserved C-terminal cysteine (the resolving cysteine), which can then be reduced by thioredoxin. This differs from the typical 2-cys PRX which resolves the oxidized cysteine by forming an intermolecular disulfide bond with the resolving cysteine from the other subunit of the homodimer. Atypical 2-cys PRX homodimers have a loop-based interface (A-type for alternate), in contrast with the B-type interface of typical 2-cys and 1-cys PRXs.
Comment:Deprotonation of the catalytic cysteine thiol is facilitated by H-bonding with the threonine or serine hydroxyl group, and the positive charge of the arginine sidechain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",