title: Activation/dephosphorylation of muscle glycogen synthase phosphorylated by phosphorylase kinase.
abstract: 1. Glycogen synthase from rabbit skeletal muscle was phosphorylated by phosphorylase kinase to yield synthase b2. 2. Dephosphorylation and activation of synthase b2 by the catalytic subunits of protein phosphatase-1 (PP-1c) and protein phosphatase-2A (PP-2Ac) was studied. The apparent Km of PP-1c and PP-2Ac were 3.3 microM and 6.2 microM, respectively. The apparent Vmax of PP-1c was about two times larger than that of PP-2Ac. 3. Ligands with phosphate moiety (AMP, glucose-6-P at high concentration) caused an inhibition in dephosphorylation by both phosphatases. Spermine inhibited the dephosphorylation by PP-1c and stimulated the action of PP-2Ac. Therefore it can be employed to distinguish the phosphatases using synthase b2 as substrate.
authors.affiliation: Department of Medical Chemistry, University School of Medicine, Debrecen, Hungary.
authors.forename: I
authors.initials: I
authors.lastname: Farkas
authors.forename: P
authors.initials: P
authors.lastname: Gergely
mesh_terms: D000818:Animals; D004789:Enzyme Activation; D006006:Glycogen Synthase / Q000378:metabolism*; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D010764:Phosphorylase Kinase / Q000378:metabolism*; D010766:Phosphorylation; D011817:Rabbits; D013379:Substrate Specificity
chemical_list: D006006:Glycogen Synthase; D010764:Phosphorylase Kinase