Epinephrine activation of phosphofructokinase in perfused rat heart independent of changes in effector concentrations.
Phosphofructokinase was determined at low substrate concentration using a new isotopic assay in extracts of perfused rat heart. Epinephrine treatment of the perfused heart resulted in an activation of the enzyme. Half-maximal activation of phosphofructokinase occurred at 5 X 10(-7) M epinephrine, which was approximately that required to produce half-maximal activation of phosphorylase. Time course studies indicated that epinephrine-mediated changes in beating rate, cyclic AMP concentration, and phosphorylase a activity were maximal at 1 to 2 min and preceded maximal activation of phosphofructokinase by approximately 3 min. the activated form of the enzyme as expressed in heart extracts was sensitized to the activators, cyclic AMP, AMP, glucose 1,6-bisphosphate, and fructose 1,6-bisphosphate. Passage of control extract that was untreated, activated by AMP, or inhibited by citrate through Sephadex G-25 columns gave eluate activities approaching control extract values. The epinephrine-activated form of the enzyme remained activated following similar treatment. The data suggest that epinephrine mediates a modification of phosphofructokinase that is independent of changes in intracellular effector concentration.
D000249:Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D004789:Enzyme Activation; D004837:Epinephrine / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D010477:Perfusion; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D006005:Phosphorylases / Q000378:metabolism; D051381:Rats
D000249:Adenosine Monophosphate; D006005:Phosphorylases; D010732:Phosphofructokinase-1; D004837:Epinephrine