Different effects of glucagon and epinephrine on the kinetic properties of liver glycogen synthase.
Kinetic constants of glycogen synthase (M0.5 for glucose-6-P and S0.5 for UDP-glucose) were determined after hepatocytes isolated from starved rats were incubated with either glucagon or epinephrine. Incubation with these hormones resulted in an increase in both S0.5 and M0.5. However, the action of glucagon resulted in great modifications on S0.5 whereas epinephrine affected mainly M0.5. Therefore, glucagon and epinephrine alter the kinetic properties of glycogen synthase provoke the phosphorylation of glycogen synthase at different site(s) acting through different mechanisms.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004837:Epinephrine / Q000494:pharmacology*; D005934:Glucagon / Q000494:pharmacology*; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000378:metabolism; D006006:Glycogen Synthase / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000201:enzymology; D014532:Uridine Diphosphate Glucose / Q000378:metabolism
D005958:Glucosephosphates; D019298:Glucose-6-Phosphate; D005934:Glucagon; D006006:Glycogen Synthase; D014532:Uridine Diphosphate Glucose; D004837:Epinephrine