Effect of glucose-6-P on the catalytic and structural properties of glycogen phosphorylase a.
Kinetic studies of muscle phosphorylase a in cationic buffer (pH 6.8) demonstrate that glucose-6-P competitively inhibits the binding of the substrate, glucose-1-P, to the enzyme. The inhibitory effect of glucose-6-P is largely overcome by glycerol-2-P. AMP counteracts inhibition of the enzyme by glucose-6-P, while glucose and glucose-6-P can interact to produce a synergistic inhibition of phosphorylase a activity. Preincubation of phosphorylase a with glucose-6-P at 20 degrees C results in approximately 3-fold increase in activity, while ultracentrifugation experiments carried out under the same conditions showed that phosphorylase a can be converted to dimers by glucose-6-P.
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D001667:Binding, Competitive; D002384:Catalysis; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000494:pharmacology*; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D010762:Phosphorylase a / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D006005:Phosphorylases / Q000037:antagonists & inhibitors*; D011817:Rabbits
D005958:Glucosephosphates; D019298:Glucose-6-Phosphate; D010762:Phosphorylase a; D006005:Phosphorylases