Glucose-6-phosphate stimulation of human muscle glycogen synthase phosphatase.
The influence of glucose-6-phosphate (glucose-6-P) on skeletal muscle glycogen synthase phosphatase was examined in normal glucose-tolerant Southwest American Indians. Phosphatase was stimulated with physiological concentrations of glucose-6-P and inhibited by ATP (5 mmol/L) and glycogen (0.1%). Phosphatase activity was measured before and after insulin infusion using the euglycemic clamp technique. Although glycogen synthase fractional activity increased in all subjects, this increase was not related to a change in phosphatase activity in the absence or presence of glucose-6-P. These results suggest that glycogen synthase phosphatase from human muscle can be regulated by physiological concentrations of glucose-6-P, ATP, and glycogen, and that insulin does not alter glucose-6-P stimulation of the enzyme in normal subjects.
Okubo
M
M
Clinical Diabetes and Nutrition Section, National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, AZ 85016.
Bogardus
C
C
Lillioja
S
S
Mott
D M
DM
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000328:Adult; D005260:Female; D019298:Glucose-6-Phosphate; D005958:Glucosephosphates / Q000494:pharmacology*; D006003:Glycogen / Q000494:pharmacology; D006007:Glycogen-Synthase-D Phosphatase / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008297:Male; D009132:Muscles / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*
D005958:Glucosephosphates; D007328:Insulin; D019298:Glucose-6-Phosphate; D000255:Adenosine Triphosphate; D006003:Glycogen; D010749:Phosphoprotein Phosphatases; D006007:Glycogen-Synthase-D Phosphatase