Glycogenin

protein
Name=glycogenin 1
caption=


width=
HGNCid=4699
Symbol=GYG1
AltSymbols=GYG
EntrezGene=2992
OMIM=603942
RefSeq=NM_004130
UniProt=P46976
PDB=
ECnumber=
Chromosome=3
Arm=q
Band=24
LocusSupplementaryData=-q25.1protein
Name=glycogenin 2
caption=


width=
HGNCid=4700
Symbol=GYG2
AltSymbols=
EntrezGene=8908
OMIM=300198
RefSeq=NM_003918
UniProt=O15488
PDB=
ECnumber=
Chromosome=X
Arm=p
Band=22.3
LocusSupplementaryData=

Glycogenin is an enzyme involved in glycogen biosynthesis. This enzyme was discovered by Dr. William J. Whelan, a fellow of the Royal Society of London and current professor of Biochemistry at the University of Miami. It is a homodimer of 37-kd subunits and is classified as a glycosyltransferase.

Function

The main enzyme involved in glycogen polymerisation. Glycogen synthase can only add to an existing chain of at least 8 glucose residues. Glycogenin acts as the primer, to which further glucose monomers may be added. It achieves this by catalyzing the addition of glucose to itself (autocatalysis) by first binding glucose from UDP-glucose to the hydroxyl group of Tyr-194. Seven more glucoses can be added, each derived from UDP-glucose, by glycogenin's glucosyltransferase activity. Once sufficient residues have been added, glycogen synthase takes over extending the chain. Glycogenin remains covalently attached to the reducing end of the glycogen molecule. Evidence accumulates that a priming protein may be a fundamental property of polysaccharide synthesis in general, the molecular details of mammalian glycogen biogenesis may serve as a useful model for other systems.

External links

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