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ENZYME entry: EC

Accepted Name
glycogenin glucosyltransferase.
Alternative Name(s)
priming glucosyltransferase.
Reaction catalysed
  • L-tyrosyl-[glycogenin] + UDP-alpha-D-glucose <=> alpha-D-glucosyl-L-tyrosyl-[glycogenin] + H(+) + UDP
  • [1,4-alpha-D-glucosyl](n)-L-tyrosyl-[glycogenin] + UDP-alpha-D-glucose <=> [1,4-alpha-D-glucosyl](n+1)-L-tyrosyl-[glycogenin] + H(+) + UDP
  • The first reaction of this enzyme is to catalyze its own glucosylation, normally at a specific Tyr of the protein if this group is free; when the Tyr is replaced by Thr or Phe, the enzyme's self-glucosylation activity is lost but its intermolecular transglucosylation ability remains.
  • 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
  • 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. hydrolyzing 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.
  • Formerly EC
PRIAM enzyme-specific profiles2.4.1.186
KEGG Ligand Database for Enzyme Nomenclature2.4.1.186
IUBMB Enzyme Nomenclature2.4.1.186
MEDLINEFind literature relating to
Rhea expert-curated reactions2.4.1.186
A7A018, GLG1_YEAS7;  P36143, GLG1_YEAST;  A6ZQJ2, GLG2_YEAS7;  
P47011, GLG2_YEAST;  O15488, GLYG2_HUMAN;  P46976, GLYG_HUMAN;  
Q9R062, GLYG_MOUSE;  P13280, GLYG_RABIT;  O08730, GLYG_RAT;  

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