Peroxiredoxin （Prx） is a growing peroxidase family，whose mammalian members have been known to connect with cell proliferation，differentiation，and apoptosis. Many isoforms （about 50 proteins），collected in accordance to the amino acid sequence homology，particularly amino-terminal region containing active site cysteine residue，and the thiol-specific antioxidant activity，distribute throughout all the kingdoms. Among them，mammalian Prx consists of 6 different members grouped into typical 2-Cys，atypical 2-Cys Prx，and 1-Cys Prx. Except Prx VI belonging to 1-Cys Prx subgroup，the other five 2-Cys Prx isotypes have the thioredoxin-dependent peroxidase （TPx） activity utilizing thioredoxin，thioredoxin reductase，and NADPH as a reducing system. Mammalian Prxs are 20 – 30 kDa in molecular size and vary in subcellular localization: Prx I，II，and VI in cytosol，Prx III in mitochondria，Prx IV in ER and secretion，Prx V showing complicated distribution including peroxisome，mitochondria and cytosol. Prx II is involved in redox regulation of the cell. Reduces peroxides with reducing equivalents provided through the thioredoxin system. It is not able to receive electrons from glutaredoxin. May play an important role in eliminating peroxides generated during metabolism. Might participate in the signaling cascades of growth factors and tumor necrosis factor-alpha by regulating the intracellular concentrations of H2O2.
