ENZYME

A new class EC 7, Translocases, has been added to the EC list. It will be part of ENZYME from release 2018_10. Read more about EC 7 here.

ENZYME entry: EC 2.4.1.186

Accepted Name

Glycogenin glucosyltransferase.

Alternative Name(s)

Glycogenin.

Priming glucosyltransferase.

Reaction catalysed

UDP-alpha-D-glucose + glycogenin <=> UDP + alpha-D-glucosylglycogenin

Cofactor(s)

Mn(2+).

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

UniProtKB/Swiss-Prot

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