title: Glutathione-thiyl radical scavenging and transferase properties of human glutaredoxin (thioltransferase). Potential role in redox signal transduction.
abstract: Glutaredoxin (GRx, thioltransferase) is implicated in cellular redox regulation, and it is known for specific and efficient catalysis of reduction of protein-S-S-glutathione-mixed disulfides (protein-SSG) because of its remarkably low thiol pK(a) ( approximately 3.5) and its ability to stabilize a catalytic S-glutathionyl intermediate (GRx-SSG). These unique properties suggested that GRx might also react with glutathione-thiyl radicals (GS(.)) and stabilize a disulfide anion radical intermediate (GRx-SSG), thereby facilitating the conversion of GS(.) to GSSG or transfer of GS(.) to form protein-SSG. We found that GRx catalyzes GSSG formation in the presence of GS-thiyl radical generating systems (Fe(2+)/ADP/H(2)O(2) + GSH or horseradish peroxidase/H(2)O(2) + GSH). Catalysis is dependent on O(2) and results in concomitant superoxide formation, and it is distinguished from glutathione peroxidase-like activity. With the horseradish peroxidase system and [(35)S]GSH, GRx enhanced the rate of GS-radiolabel incorporation into GAPDH. GRx also enhanced the rate of S-glutathionylation of glyceraldehyde-3-phosphate dehydrogenase with GSSG or S-nitrosoglutathione, but these glutathionyl donors were much less efficient. Both actin and protein-tyrosine phosphatase-1B were superior substrates for GRx-facilitated S-glutathionylation with GS-radical. These studies characterize GRx as a versatile catalyst, facilitating GS-radical scavenging and S-glutathionylation of redox signal mediators, consistent with a critical role in cellular regulation.
authors.affiliation: Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Starke
authors.forename: P Boon
authors.initials: PB
authors.lastname: Chock
authors.forename: John J
authors.initials: JJ
authors.lastname: Mieyal
mesh_terms: D002384:Catalysis; D003574:Cytochrome c Group / Q000378:metabolism; D016166:Free Radical Scavengers / Q000378:metabolism*; D054477:Glutaredoxins; D005978:Glutathione / Q000378:metabolism*; D019803:Glutathione Disulfide / Q000378:metabolism; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism* / Q000502:physiology; D010100:Oxygen / Q000494:pharmacology; D011490:Protein Disulfide Reductase (Glutathione)
chemical_list: D003574:Cytochrome c Group; D016166:Free Radical Scavengers; D054477:Glutaredoxins; D010088:Oxidoreductases; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D011490:Protein Disulfide Reductase (Glutathione); D005978:Glutathione; D010100:Oxygen; D019803:Glutathione Disulfide