On the mechanism of inactivation of muscle glycogen phosphorylase by insulin.
Glucose 6-phosphate, an allosteric inhibitor of skeletal muscle phosphorylase b, inhibits at physiological concentrations and conditions the phosphorylation and activation of the enzyme by phosphorylase b kinase. AMP inhibits the dephosphorylation of phosphorylase a, but is without effect on the phosphorylation of phosphorylase b. Glucose 6-phosphate has no effect on the activity of phosphorylase a and does not affect its dephosphorylation by phosphatases 1 or 2A. The inhibition of the phosphorylation of phosphorylase b by glucose 6-phosphate may explain the reported decreased phosphorylation of phosphorylase in muscle following insulin treatment, which elevates intracellular levels of glucose 6-phosphate.
Villar-Palasi
C
C
Department of Pharmacology, Medical School, University of Virginia, Charlottesville 22908.
D000818:Animals; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000201:enzymology; D006005:Phosphorylases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar
D005958:Glucosephosphates; D007328:Insulin; D019298:Glucose-6-Phosphate; D006005:Phosphorylases