Glycogenin
2213219
207756637
2008-04-24T02:05:08Z
192.88.124.206
{{protein
|Name=glycogenin 1
|caption=
|image=
|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=-q25.1
}}
{{protein
|Name=glycogenin 2
|caption=
|image=
|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 [[monomer]]s may be added. It achieves this by [[catalysis|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==
* {{MeshName|glycogenin}}
{{enzyme-stub}}
[[de:Glycogenin]]