Glycogenin

• OMIM: 603 942
• UniProt: P46976

Glycogenin called enzymes that attach themselves glucose residues - the polysaccharide can be up to 13 glucose units long. This reaction is necessary to make the production of long-chain polysaccharides, in particular glycogen, in motion, as the enzyme glycogen synthase can work only if short chains are already present. Glycogenine there in fungi and metazoans. People have two homologous genes which allow for several isoforms of the enzyme, which are located in different tissue types. Glycogenin is tightly bound to glycogen, so it can be referred to as their cofactor. Mutations in GYG1 gene are responsible for a hereditary glycogen storage disease.

Catalyzed reactions

Glycogenin

Glycogenin catalyzes the addition of glucose to itself, by binding the first UDP -glucose formed from UTP and glucose to the Tyr -194 residue of its active site. This creates UDP.

Thereafter the enzyme is classified in more glucose residues up to a certain limit ( approximately 5-13), on reaching which glycogen synthase takes over the further polymerization. The glycogenin remains bound to the Glycogenkette. After the possible degradation of the chain, the enzyme is available as a nucleus for re glycogen synthesis is available, that is, it is not degraded.