Dephosphorylation of glycogen synthase from human polymorphonuclear leukocytes

Leukocyte glycogen synthase (UDPglucose:glycogen 4-alpha-d-glucosyltransferase, EC 2.4.1.11) was phosphorylated to about one P1/synthase subunit by either the cAMP-dependent protein kinase or the cAMP-dependent synthase kinase. The relationship between dephosphorylation and the increase in the ratio of independence was investigated by analysis of the release of 32P-labelled phosphopeptides from the trypsin-sensitive and the trypsin-insensitive regions. The trypsin-insensitive region was predominantly dephosphorylated and a close correlation between dephosphorylation of a phosphopeptide in the trypsin-insensitive region and activation of glycogen synthase is reported for the enzyme phosphorylated in both ways.