EC - Glycogenin glucosyltransferase

  IntEnz view ENZYME view

IntEnz Enzyme Nomenclature


Accepted name:
glycogenin glucosyltransferase
Other names:
UDP-glucose:glycogenin glucosyltransferase
priming glucosyltransferase
Systematic name:
UDP-α-D-glucose:glycogenin α-D-glucosyltransferase




The first reaction of this enzyme is to catalyse its own glucosylation, normally at Tyr-194 of the protein if this group is free. When Tyr-194 is replaced by Thr or Phe, the enzyme's Mn2+-dependent self-glucosylation activity is lost but its intermolecular transglucosylation ability remains [7]. It continues to glucosylate an existing glucosyl group until a length of about 5-13 residues has been formed. Further lengthening of the glycogen chain is then carried out by EC, glycogen (starch) synthase. The enzyme is not highly specific for the donor, using UDP-xylose in addition to UDP-glucose (although not glucosylating or xylosylating a xylosyl group so added). It can also use CDP-glucose and TDP-glucose, but not ADP-glucose or GDP-glucose. Similarly it is not highly specific for the acceptor, using water (i.e. hydrolysing UDP-glucose) among others. Various forms of the enzyme exist, and different forms predominate in different organs. Thus primate liver contains glycogenin-2, of molecular mass 66 kDa, whereas the more widespread form is glycogenin-1, with a molecular mass of 38 kDa.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0102751 , GO:0008466
CAS Registry Number: 117590-73-5
UniProtKB/Swiss-Prot: (19) [show] [UniProt]


  1. Krisman, C.R. and Barengo, R.
    A precursor of glycogen biosynthesis: α-1,4-glucan-protein.
    Eur. J. Biochem. 52 : 117-123 (1975). [PMID: 809265]
  2. Pitcher, J., Smythe, C., Campbell, D.G. and Cohen, P.
    Identification of the 38-kDa subunit of rabbit skeletal muscle glycogen synthase as glycogenin.
    Eur. J. Biochem. 169 : 497-502 (1987). [PMID: 3121316]
  3. Pitcher, J., Smythe, C. and Cohen, P.
    Glycogenin is the priming glucosyltransferase required for the initiation of glycogen biogenesis in rabbit skeletal muscle.
    Eur. J. Biochem. 176 : 391-395 (1988). [PMID: 2970965]
  4. Kennedy, L.D., Kirkman, B.R., Lomako, J., Rodriguez, I.R. and Whelan, W.J.
    The biogenesis of rabbit-muscle glycogen.
    In: Berman, M.C. and Opie, L.A. (Eds.) Membranes and Muscle , ICSU Press/IRL Press , Oxford , 1985 , 65-84
  5. Rodriguez, I.R. and Whelan, W.J.
    A novel glycosyl-amino acid linkage: rabbit-muscle glycogen is covalently linked to a protein via tyrosine.
    Biochem. Biophys. Res. Commun. 132 : 829-836 (1985). [PMID: 4062948]
  6. Lomako, J., Lomako, W.M. and Whelan, W.J.
    A self-glucosylating protein is the primer for rabbit muscle glycogen biosynthesis.
    FASEB J. 2 : 3097-3103 (1988). [PMID: 2973423]
  7. Lomako, J., Lomako, W.M. and Whelan, W.J.
    Erratum report. A self-glucosylating protein is the primer for rabbit muscle glycogen biosynthesis.
    FASEB J. 3 : 1873 (1989).
  8. Alonso, M.D., Lomako, J., Lomako, W.M. and Whelan, W.J.
    Catalytic activities of glycogenin additional to autocatalytic self-glucosylation.
    J. Biol. Chem. 270 : 15315-15319 (1995). [PMID: 7797519]
  9. Alonso, M.D., Lomako, J., Lomako, W.M. and Whelan, W. J.
    A new look at the biogenesis of glycogen.
    FASEB J. 9 : 1126-1137 (1995). [PMID: 7672505]
  10. Mu, J. and Roach, P.J.
    Characterization of human glycogenin-2, a self-glucosylating initiator of liver glycogen metabolism.
    J. Biol. Chem. 273 : 34850-34856 (1998). [PMID: 9857012]
  11. Gibbons, B.J., Roach, P.J. and Hurley, T.D.
    Crystal structure of the autocatalytic initiator of glycogen biosynthesis, glycogenin.
    J. Mol. Biol. 319 : 463-477 (2002). [PMID: 12051921]

[EC created 1992 (EC created 1984, incorporated 2007)]