Purification and characterization of a cofactor that controls the oxidative phase of the pentose phosphate cycle in liver and other tissues of rat.
We have recently reported the presence, in rat liver, of a cofactor characterized as a protein of Mr 10(5), which cooperates with GSSG to prevent the inhibition of glucose-6-phosphate dehydrogenase by NADPH. The inhibition that this coenzyme also exerts on 6-phosphogluconate dehydrogenase is similarly prevented by a cofactor-GSSG system. The activity of the cofactor increases in the livers of rats fed on carbohydrate-rich diets. Purification of the components in rat liver homogenate by ion-exchange chromatography and preparative polyacrylamide gel electrophoresis showed that the deinhibitory effect on both dehydrogenases is exerted by the same cofactor. The purified cofactor appeared as a unique protein of Mr 37.10(3) in SDS-polyacrylamide gel electrophoresis. Rat kidney and adipose tissue were the only nonhepatic tissues showing a cofactor-GSSG deinhibitory effect on both dehydrogenases of the oxidative phase of the pentose phosphate cycle. The deinhibitory activity, also corresponding with a cellular component of Mr 10(5), was only diet-inducible in adipose tissue. The neutralization of the kidney and adipose tissue deinhibitory activity by rat liver cofactor antibodies suggested that there was a structural relationship between the cofactors prepared from these tissues.
Garcia
G
G
Department of Biochemistry and Molecular Biology, Faculty of Biology, University of Santiago, Santiago de Compostela, Spain.
Nogueira
M
M
Freire
M
M
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D002845:Chromatography; D002851:Chromatography, High Pressure Liquid; D003067:Coenzymes / Q000302:isolation & purification* / Q000378:metabolism / Q000494:pharmacology; D004040:Dietary Carbohydrates / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004912:Erythrocytes / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors; D005978:Glutathione / Q000494:pharmacology; D007525:Isoelectric Focusing; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D008970:Molecular Weight; D009249:NADP / Q000494:pharmacology; D010084:Oxidation-Reduction; D010427:Pentose Phosphate Pathway / Q000187:drug effects*; D010734:Phosphogluconate Dehydrogenase / Q000037:antagonists & inhibitors; D051381:Rats; D011919:Rats, Inbred Strains
D003067:Coenzymes; D004040:Dietary Carbohydrates; D009249:NADP; D010734:Phosphogluconate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D005978:Glutathione