title: Glutathione Is the Resolving Thiol for Thioredoxin Peroxidase Activity of 1-Cys Peroxiredoxin Without Being Consumed During the Catalytic Cycle.
abstract: OBJECTIVE
  A three-step catalytic cycle is common to all peroxiredoxins (Prxs), despite structural and kinetic differences. The second step in 1-Cys type Prxs is a matter of debate since they lack an additional cysteine to play the resolving role, as happens with the 2-Cys Prxs. The aim of this study was to elucidate the role of glutathione (GSH) in the thioredoxin-dependent peroxidase activity of Saccharomyces cerevisiae mitochondrial Prx1p, a 1-Cys type Prx.
  
  
  RESULTS
  The peroxidatic Cys91 residue of two Prx1p peptides can be linked by a disulfide, which can be reduced by thioredoxin and by GSH (Km=6.1 μM). GSH forms a mixed disulfide with the peroxidatic cysteine spontaneously in vitro and in vivo. Mitochondrial Trx3p deglutathionylates Prx1p without formation of GSSG so that GSH is not consumed in the process. The structural unit of native Prx1p is a dimer whose subunits are not covalently linked, but a hexameric assembly of three disulfide-bound dimers can also be formed.
  
  
  METHODS
  GSH is presented as a protective cofactor of Prx1p, which is not consumed during the peroxidase reaction, but provides a robust mechanism as the resolving cysteine and efficiently prevents Prx1p overoxidation. GSH exerts these roles at concentrations well below those commonly considered necessary for its antioxidant and redox buffering functions.
  
  
  CONCLUSIONS
  A 1-Cys peroxide scavenging mechanism operates in yeast mitochondria involving an autonomous glutathione molecule and the thioredoxin system, which could have universal validity. Prx1p is fairly well protected from overoxidation, questioning its role in a floodgate mechanism for H2O2 signaling.
authors.affiliation: 1 Biochemistry and Cellular Signaling Group, Department of Experimental Biology, University of Jaén , Jaén, Spain .
authors.forename: José Rafael
authors.initials: JR
authors.lastname: Pedrajas
authors.affiliation: 2 MRC-Arthritis Research UK Centre for Integrated Research into Musculoskeletal Aging (CIMA), Skeletal Muscle Pathophysiology Group, Institute of Ageing and Chronic Disease, University of Liverpool , Liverpool, United Kingdom .
authors.forename: Brian
authors.initials: B
authors.lastname: McDonagh
authors.affiliation: 3 Cardiovascular Research Group, Department of Experimental Biology, University of Jaén , Jaén, Spain .
authors.forename: Francisco
authors.initials: F
authors.lastname: Hernández-Torres
authors.affiliation: 4 Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla , Sevilla, Spain .
authors.forename: Antonio
authors.initials: A
authors.lastname: Miranda-Vizuete
authors.affiliation: 5 Department of Biochemistry and Molecular Biology, University of Córdoba , Córdoba, Spain .|6 Córdoba Maimónides Institute for Biomedical Research , IMIBIC, Córdoba, Spain .
authors.forename: Raúl
authors.initials: R
authors.lastname: González-Ojeda
authors.affiliation: 5 Department of Biochemistry and Molecular Biology, University of Córdoba , Córdoba, Spain .|6 Córdoba Maimónides Institute for Biomedical Research , IMIBIC, Córdoba, Spain .
authors.forename: Emilia
authors.initials: E
authors.lastname: Martínez-Galisteo
authors.affiliation: 5 Department of Biochemistry and Molecular Biology, University of Córdoba , Córdoba, Spain .|6 Córdoba Maimónides Institute for Biomedical Research , IMIBIC, Córdoba, Spain .
authors.forename: C Alicia
authors.initials: CA
authors.lastname: Padilla
authors.affiliation: 5 Department of Biochemistry and Molecular Biology, University of Córdoba , Córdoba, Spain .|6 Córdoba Maimónides Institute for Biomedical Research , IMIBIC, Córdoba, Spain .
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Bárcena
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D002384:Catalysis; D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007700:Kinetics; D008928:Mitochondria / Q000378:metabolism; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013879:Thioredoxins / Q000378:metabolism
chemical_list: D000975:Antioxidants; D004220:Disulfides; D029701:Saccharomyces cerevisiae Proteins; C541128:Trx3 protein, S cerevisiae; D013879:Thioredoxins; D006861:Hydrogen Peroxide; C410041:PRX1 protein, S cerevisiae; D010544:Peroxidases; D005978:Glutathione; D003545:Cysteine