Peroxiredoxins (Prxs) are a ubiquitous family of antioxidant proteins. They can be divided into three classes: typical 2-Cys, atypical 2-Cys and 1-Cys peroxiredoxins . The peroxidase reaction comprises two steps centred around a redox-active cysteine called the peroxidatic cysteine. All three peroxiredoxin classes have the first step in common, in which the peroxidatic cysteine attacks the peroxide substrate and is oxidized to S-hydroxycysteine (a sulfenic acid) (see {single/111115a::mechanism}). The second step of the peroxidase reaction, the regeneration of cysteine from S-hydroxycysteine, distinguishes the three peroxiredoxin classes. For typical 2-Cys Prxs, in the second step, the peroxidatic S-hydroxycysteine from one subunit is attacked by the 'resolving' cysteine located in the C-terminus of the second subunit, to form an intersubunit disulfide bond, which is then reduced by one of several cell-specific thiol-containing reductants completing the catalytic cycle. In the atypical 2-Cys Prxs, both the peroxidatic cysteine and its resolving cysteine are in the same polypeptide, so their reaction forms an intrachain disulfide bond. The 1-Cys Prxs conserve only the peroxidatic cysteine, so its regeneration involves direct interaction with a reductant molecule. Glutathione-dependent peroxiredoxins have been reported from bacteria and animals, and appear to be 1-Cys enzymes. The mechanism for the mammalian PRDX6 enzyme involves heterodimerization of the enzyme with pi-glutathione S-transferase, followed by glutathionylation of the oxidized cysteine residue. Subsequent dissociation of the heterodimer yields glutathionylated peroxiredoxin, which is restored to the active form via spontaneous reduction by a second glutathione molecule.
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SYSTEMATIC NAME
IUBMB Comments
glutathione:hydroperoxide oxidoreductase
Peroxiredoxins (Prxs) are a ubiquitous family of antioxidant proteins. They can be divided into three classes: typical 2-Cys, atypical 2-Cys and 1-Cys peroxiredoxins [1]. The peroxidase reaction comprises two steps centred around a redox-active cysteine called the peroxidatic cysteine. All three peroxiredoxin classes have the first step in common, in which the peroxidatic cysteine attacks the peroxide substrate and is oxidized to S-hydroxycysteine (a sulfenic acid) (see {single/111115a::mechanism}). The second step of the peroxidase reaction, the regeneration of cysteine from S-hydroxycysteine, distinguishes the three peroxiredoxin classes. For typical 2-Cys Prxs, in the second step, the peroxidatic S-hydroxycysteine from one subunit is attacked by the 'resolving' cysteine located in the C-terminus of the second subunit, to form an intersubunit disulfide bond, which is then reduced by one of several cell-specific thiol-containing reductants completing the catalytic cycle. In the atypical 2-Cys Prxs, both the peroxidatic cysteine and its resolving cysteine are in the same polypeptide, so their reaction forms an intrachain disulfide bond. The 1-Cys Prxs conserve only the peroxidatic cysteine, so its regeneration involves direct interaction with a reductant molecule. Glutathione-dependent peroxiredoxins have been reported from bacteria and animals, and appear to be 1-Cys enzymes. The mechanism for the mammalian PRDX6 enzyme involves heterodimerization of the enzyme with pi-glutathione S-transferase, followed by glutathionylation of the oxidized cysteine residue. Subsequent dissociation of the heterodimer yields glutathionylated peroxiredoxin, which is restored to the active form via spontaneous reduction by a second glutathione molecule.
the 1-Cys Prdx type Prdx6, possessing a single conserved cysteine residue, shows heterodimerization with piGSH S-transferase as part of the catalytic cycle, and the ability to either reduce the oxidized sn-2 fatty acyl group of phospholipids (peroxidase activity) or to hydrolyze the sn-2 ester (alkyl) bond of phospholipids (PLA2 activity), thus exhiting peroxidase and phospholipase activities, overview. The bifunctional protein has separate active sites for both activities, namely a Cys 47-dependent peroxidase activity site and a Ser32-dependent PLA2 activity site. Substrate specificity, overview
DTT is not a physiological reductant and thioredoxin, the reductant that is active in the catalytic cycle for the 2-Cys peroxiredoxins, is not effective as a reductant for 1-Cys Prdx6. Prdx6 binds and reduces phospholipid hydroperoxides. Prdx6 reduces H2O2 and other short chain hydroperoxides. The conserved Cys in Prdx6 is buried at the base of a narrow pocket. This location renders it unable to dimerize through disulfide formation in the native configuration but homodimers (and multimers) can arise through hydrophobic interactions. Disulfide formation may occur with denatured proteins and heterodimerization also occurs normally as part of the catalytic cycle. The protein also contains a surface expressed catalytic triad, S-D-H, that is important for phospholipid binding and enzymatic activities
the 1-Cys Prdx type Prdx6, possessing a single conserved cysteine residue, shows heterodimerization with piGSH S-transferase as part of the catalytic cycle, and the ability to either reduce the oxidized sn-2 fatty acyl group of phospholipids (peroxidase activity) or to hydrolyze the sn-2 ester (alkyl) bond of phospholipids (PLA2 activity), thus exhiting peroxidase and phospholipase activities, overview. The bifunctional protein has separate active sites for both activities, namely a Cys 47-dependent peroxidase activity site and a Ser32-dependent PLA2 activity site. Substrate specificity, overview
High intensity of cytoplasmic peroxiredoxin VI expression is associated with adverse outcome in diffuse large B-cell lymphoma independently of International Prognostic Index.
High intensity of cytoplasmic peroxiredoxin VI expression is associated with adverse outcome in diffuse large B-cell lymphoma independently of International Prognostic Index.
within organs, expression of Prdx is greatest in epithelium such as apical regions of respiratory epithelium and skin epidermis, tissue distribution, overview
cytosolic Prdx6 could bind to and reduce peroxidized membrane phospholipids followed by its dissociation from the membrane and return to the cytosolic compartment
peroxiredoxin 6 down-regulation reduces cell proliferation. Enzyme silencing interferes with apoptotic signaling from CD95 but does not induce apoptosis in HepG2 cells
Prdx6 has important roles in both antioxidant defense based on its ability to reduce peroxidized membrane phospholipids and in phospholipid homeostasis based on its ability to generate lysophospholipid substrate for the remodeling pathway of phospholipid synthesis
regulation of Prdx6 gene regulation, overview. Transcription is activated by binding of the transcription factor Nrf2 to the ARE whereas transcription is inhibited by the binding of Nrf3. Prdx6 expression also is responsive to hormonal regulation
function of PRDX6 in osteogenic differentiation, bone regeneration, and bone development. It is proposed that PRDX6 is a critical enzyme for cell fate determination of dental pulp stem cell into osteoblast lineages
Prdx6 plays crucial roles in lung phospholipid metabolism, lipid peroxidation repair, and inflammatory signaling. Prdx6 prevents oxidative stress in human retinal pigment epithelial cells by activating the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) pathway. Prdx6 is necessary to prevent cataract formation and to limit aging-induced oxidative stress in the eye
MAP kinase mediated phosphorylation of Prdx6 at residue T177, results in increased phospholipase A2 activity, but phosphorylation has no effect on the peroxidase activity of Prdx6
oxidant stress is, e.g. by H2O2, paraquat, a potent inducer of Prdx6 expression and stimulates Prdx6 gene expression by a transcriptional mechanism involving its antioxidant response element, ARE