title: Regulation of hepatic phosphofructokinase by 6-phosphogluconate.
abstract: 6-Phosphogluconate activates phosphofructokinase in extracts of rat liver by decreasing both the apparent S0.5 for fructose 6-phosphate and the degree of cooperative binding of fructose 6-phosphate. There is no effect on the maximum velocity. Enzyme activity is a hyperbolic function of the concentration of 6-phosphogluconate, and the apparent Km is 60 microM. Thus, a substantial activation of the enzyme is achieved with a physiological concentration of 6-phosphogluconate (40 microM). Activation of phosphofructokinase by 6-phosphogluconate is influenced by a low molecular weight factor(s) in liver extracts. Part of the influence may be attributed to fructose 2,6-bisphosphate which, in some conditions, acts synergistically with 6-phosphogluconate to activate phosphofructokinase. In the presence of a mixture of ATP, ADP, and AMP at physiological concentrations, the effects of 6-phosphogluconate (40 and 200 microM) and a saturating concentration of fructose 2,6-bisphosphate (400 nM) are more nearly additive. This result suggests that 6-phosphogluconate and fructose 2,6-bisphosphate act at different sites on the enzyme and that 6-phosphogluconate may contribute to the physiological regulation of hepatic phosphofructokinase. Regulation of phosphofructokinase by 6-phosphogluconate may provide a means by which the disposition of glucose 6-phosphate between the oxidative branch of the hexosemonophosphate pathway and glycolysis can be coordinated, an effect which may be important during hepatic lipogenesis.
mesh_terms: D000818:Animals; D004347:Drug Interactions; D004789:Enzyme Activation / Q000187:drug effects; D005635:Fructosediphosphates / Q000494:pharmacology; D005636:Fructosephosphates / Q000378:metabolism; D005942:Gluconates / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013403:Sugar Phosphates / Q000494:pharmacology*
chemical_list: D005635:Fructosediphosphates; D005636:Fructosephosphates; D005942:Gluconates; D013403:Sugar Phosphates; C027618:fructose-6-phosphate; C027652:fructose 2,6-diphosphate; D010732:Phosphofructokinase-1; C008884:6-phosphogluconic acid