title: The initiation of glycogen biosynthesis in rat heart alpha-1,4 glucans tightly associated with glycogen synthase.
abstract: A partially purified glycogen synthase from rat cardiac muscle transferred glucosyl residues from UDP-[14C]glucose to an endogenous protein acceptor in the absence of added primer. After native gel electrophoresis of the enzyme preparation, unprimed activity was detected. Primer-dependent and independent activities were found in the same position. After denaturing gel electrophoresis of the reaction products, radioactivity comigrated with protein. Pulse-chase experiments showed that the size of the reaction products increased as a function of time. These products were degraded by amyloglucosidase, thus suggesting that glycogen-like molecules had grown on the protein acceptor. The activity of the enzyme was markedly reduced upon preincubation with alpha-amylase. Therefore, preformed protein-bound alpha-1,4-glucans were acting as primers. The glucoprotein acceptor may be a protein strongly associated with glycogen synthase, or alternatively, the enzyme itself.
authors.forename: M L
authors.initials: ML
authors.lastname: Blumenfeld
authors.forename: C R
authors.initials: CR
authors.lastname: Krisman
mesh_terms: D000818:Animals; D001665:Binding Sites; D004591:Electrophoresis, Polyacrylamide Gel; D005936:Glucans / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000096:biosynthesis*; D006006:Glycogen Synthase / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D012995:Solubility; D000516:alpha-Amylases
chemical_list: D005936:Glucans; D006003:Glycogen; C040088:1,4-glucan; D006006:Glycogen Synthase; D000516:alpha-Amylases; D005947:Glucose