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]]