Muscle Glycogen Synthetase in Normal Subjects

The relationship between muscle glycogen level and glycogen synthetase activity was studied in normal man. Under basal conditions 27% of the total activity was in the I form. Lowering glycogen by exercise increased I activity to 75%. As glycogen increased back to basal level during carbohydrate feeding, I activity decreased to 25%. Increase of glycogen above normal level did not further affect I activity. Total activity remained unchanged. An inverse relationship between glycogen level and per cent I activity was established in human muscle.