title: Hydrogen peroxide increases the activity of gamma-glutamylcysteine synthetase in cultured Chinese hamster V79 cells.
abstract: Hydrogen peroxide (H2O2) caused a rapid and a concentration-dependent increase in the activity of gamma-glutamylcysteine synthetase (gamma-GCS) in cultured Chinese hamster V79 cells. The increase in the activity was transient and declined rapidly during post-treatment incubation. Inhibition of protein synthesis by cycloheximide, chelation of divalent iron by o-phenanthroline, and scavenging of free radicals by butyl-4-hydroxyanisole failed to suppress the increase in activity of gamma-GCS caused by H2O2. However, catalase completely inhibited the increase in the activity of the enzyme. H2O2 did not change the level of total glutathione (GSH + GSSG) but it oxidized GSH. The increase in levels of GSSG caused by H2O2 was enhanced by o-phenanthroline. These results suggest that the increase in activity of gamma-GCS caused by H2O2 is not an inducible phenomenon, nor it is attributable to the action of free radicals generated by an iron-catalyzed Fenton reaction. Furthermore, the changes in levels of GSH and GSSG caused by H2O2 appear not to be responsible for the increase in activity of gamma-GCS caused by the hydroperoxide. However, chemical reduction of the enzyme, the activity of which had been increased by H2O2, resulted in a decrease in tha activity, suggesting the involvement of oxidation of the enzyme in the increased activity of gamma-GCS caused by H2O2. The results also suggest that the activity of gamma-GCS in cultured V79 cells can be regulated by the cellular oxidation-reduction state.
authors.affiliation: Department of Environmental Toxicology, Faculty of Pharmaceutical Sciences, Teikyo University, Kanagawa, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Ochi
mesh_terms: D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004789:Enzyme Activation / Q000187:drug effects; D005347:Fibroblasts / Q000201:enzymology; D005721:Glutamate-Cysteine Ligase / Q000187:drug effects* / Q000378:metabolism*; D005978:Glutathione / Q000187:drug effects / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008168:Lung; D008297:Male; D010084:Oxidation-Reduction / Q000187:drug effects; D010618:Phenanthrolines / Q000494:pharmacology
chemical_list: D010618:Phenanthrolines; D006861:Hydrogen Peroxide; D005721:Glutamate-Cysteine Ligase; D005978:Glutathione; C025205:1,10-phenanthroline