title: Oxidized forms of ovine erythrocyte glutathione peroxidase. Cyanide inhibition of a 4-glutathione:4-selenoenzyme.
abstract: [75Se]Glutathione peroxidase (glutathione:hydrogen-peroxide oxidoreductase, EC 1.11.1.9) containing 4 mol selenium per mol was isolated in 33% yield using 10% ethanol to stabilize the purified enzyme. When reduced with GSH and rapidly separated from GSH by gel filtration chromatography, GSH peroxidase was eluted in a labile oxidized (iodoacetate-insensitive) form which was stable at 4 degrees C but unstable at 25 degrees C (form A). When GSH-reduced enzyme was allowed to oxidize in the course of dialysis a more stable oxidized form was obtained (form C) which was rapidly inactivated by cyanide. Using [35S]GSH, form C was shown to contain tightly bound glutathione in approx. equimolar ratio with selenium. The cyanide sensitivity of GSH  peroxidase is therefore correlated with the presence of a glutathione moiety in the enzyme. The isolation of GSH peroxidase containing bound glutathione suggests that intermediates containing glutathione bound to selenium may be formed during the catalytic cycle.
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D003486:Cyanides; D004912:Erythrocytes / Q000201:enzymology* / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000037:antagonists & inhibitors / Q000097:blood*; D007461:Iodoacetates; D010544:Peroxidases / Q000097:blood*; D012643:Selenium / Q000378:metabolism; D012756:Sheep
chemical_list: D003486:Cyanides; D007461:Iodoacetates; D010544:Peroxidases; D005979:Glutathione Peroxidase; D005978:Glutathione; D012643:Selenium