Glycogen, a branched polymer of glucose, is a storage molecule whose accumulation is under rigorous control in many cells. In Saccharomyces cerevisiae, glycogen biosynthesis involves three processes: nucleation, elongation, and branching (also known as ramification). The formation of glycogen begins when either Glg1p or Glg2p uses UDP-glucose to self-glucosylate to produce a short alpha (1,4)-glucosyl chain covalently attached to one of their internal tyrosine residues. After the self-glucosylation of Glg1p or Glg2p, glycogen synthase is able to extend the linear alpha (1,4)-glucosyl chains of glycogen by catalyzing the formation of alpha (1,4)-glucosidic bonds from UDP- glucose at the non-reducing ends. Branches can be added into the glycogen molecule by Glc3p, which is the glycogen branching enzyme (EC:2.4.1.18) in S. cerevisiae. d5f afc a2e a83 R = a glycogenin R = a glycogenin glycogen biosynthetic pathway PW:0000532 Pathway Ontology glucose utilization pathway PW:0000555 Pathway Ontology glucose conversion pathway PW:0000558 Pathway Ontology 1908457 PubMed Two glycogen synthase isoforms in Saccharomyces cerevisiae are coded by distinct genes that are differentially controlled. J Biol Chem 1991 Farkas I Hardy TA Goebl MG Roach PJ 11152943 PubMed Reserve carbohydrates metabolism in the yeast Saccharomyces cerevisiae. FEMS Microbiol Rev 2001 François J Parrou JL 8900126 PubMed Initiation of glycogen synthesis in yeast. Requirement of multiple tyrosine residues for function of the self-glucosylating Glg proteins in vivo. J Biol Chem 1996 Mu J Cheng C Roach PJ 1634552 PubMed Coordinate regulation of glycogen metabolism in the yeast Saccharomyces cerevisiae. Induction of glycogen branching enzyme. J Biol Chem 1992 Thon VJ Vigneron-Lesens C Marianne-Pepin T Montreuil J Decq A Rachez C Ball SG Cannon JF