title: A critical appraisal of the effect of oxidized glutathione on hepatic glucose 6-phosphate dehydrogenase activity.
abstract: Experiments were undertaken to elucidate the mechanism of the reversal of NADPH inhibition of rat liver glucose 6-phosphate dehydrogenase by oxidized gluthathione alone and in combination with a putative cofactor described by Eggleston & Krebs [(1974) Biochem. J. 138, 425-435]. Evidence is presented that this reversal is largely an artifact, caused by the incorrect application of a control assay procedure and a spurious effect of Zn2+ (added in order to inhibit glutathione reductase) in crude enzyme solutions. When the proper assay procedure is used and glutathione reductase is inhibited with low concentrations of Hg2+, glutathione addition has no effect on NADPH inhibition of glucose 6-phosphate dehydrogenase. No evidence was found for the existence of a cofactor that mediates an effect of glutathione on glucose 6-phosphate dehydrogenase.
mesh_terms: D000818:Animals; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005978:Glutathione / Q000031:analogs & derivatives* / Q000494:pharmacology; D019803:Glutathione Disulfide; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008628:Mercury / Q000494:pharmacology; D009249:NADP / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D015032:Zinc / Q000494:pharmacology
chemical_list: D009249:NADP; D005954:Glucosephosphate Dehydrogenase; D008628:Mercury; D005978:Glutathione; D015032:Zinc; D019803:Glutathione Disulfide