title: Inactivation of phosphofructokinase by glucagon in rat hepatocytes.
abstract: Kinetic evidence of a time- and dose-dependent inactivation of phosphofructokinase by glucagon in isolated rat hepatocytes is reported. This inactivation, which persists after gel filtration of a cell-free extract on Sephadex G-25 and after 400-fold purification of the enzyme on agarose-ATP, is observed when the enzyme activity is measured at subsaturating concentrations of fructose 6-phosphate, while there is no change in Vmax. Phosphofructokinase inactivation by glucagon parallels the known inactivation of pyruvate kinase L and activation of glycogen phosphorylase alpha. Exogenous cyclic AMP mimics the effect of this hormone. Half-maximal effect for both phosphofructokinase and pyruvate kinase L is caused by a similar dose of glucagon (1 x 10(-10) M). The inactivation of phosphofructokinase by nonsaturating concentration of glucagon is reversed spontaneously within 40 min of incubation and this reversion is accelerated by insulin.
mesh_terms: D000818:Animals; D005934:Glucagon / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D010732:Phosphofructokinase-1 / Q000037:antagonists & inhibitors*; D010762:Phosphorylase a / Q000378:metabolism; D011770:Pyruvate Kinase / Q000378:metabolism; D051381:Rats
chemical_list: D005934:Glucagon; D010762:Phosphorylase a; D010732:Phosphofructokinase-1; D011770:Pyruvate Kinase