ENZYME entry: EC 2.4.1.186

Accepted Name

glycogenin glucosyltransferase

Alternative Name(s)

glycogenin

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

Comment(s)

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 2.4.1.11.
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 2.4.1.112.

Cross-references

BRENDA

EC2PDB

ExplorEnz

PRIAM enzyme-specific profiles

KEGG Ligand Database for Enzyme Nomenclature

IUBMB Enzyme Nomenclature

IntEnz

MEDLINE

MetaCyc

Rhea expert-curated reactions

UniProtKB/Swiss-Prot

All UniProtKB/Swiss-Prot entries referenced in this entry, with possibility to download in different formats, align etc.

All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 2.4.1.-
All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 2.4.-.-
All ENZYME / UniProtKB/Swiss-Prot entries corresponding to 2.-.-.-