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Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
BioCyc websites down
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Metabolic Modeling Tutorial
discounted EARLY registration ends Dec 31, 2014
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MetaCyc Transporter: glycogenin 1

Gene: GYG1 Accession Number: HS08931 (MetaCyc)

Species: Homo sapiens

Subunit composition of glycogenin 1 = [GYG1]2
         glycogenin 1 monomer = GYG1

Alternative forms of glycogenin 1 monomer: glucosyl-glycogenin-1

Summary:
The first step in the biosynthesis of the glycogen polymer is the synthesis of a glycogen primer - a short chain of glucose units connected by 1,4-α linkages. Once the primer is formed, it can be extanded and branched by the combined action of glycogen synthase and 1,4-α-glucan branching enzyme.

In mammals the glycogen primer is formed by the unique enzyme glycogenin. The enzyme is unique since it serves as both a substrate and an enzyme. It catalyzes two different reactions: in the first reaction it catalyzes the attachment of a glucosyl unit to a Tyrosine residue within the structure of a second glycogenin oligomer. In the second reaction, it catalyzes the linking of additional glucosyl units to the one attached to glycogenin, resulting in the extension of the chain. Once the chain reaches a certain length (approximately 8 glucose units) it primes the glycogen synthase reaction, which adds more glucose units, and forms, along with the branching enzyme, a much larger glycogen polymer. Glycogenin is never removed from the glucose polymer, and remains within the mature macroglycogen [Lomako04].

The first form of glycogenin, now called glycogenin 1, was discovered in muscle, and is encoded by the GYG1 gene. A second form of glycogenin was later discover in the liver of primates. That form was named glycogenin 2, and is encoded by the GYG2 gene, not present in any organism but primates [Mu97, Zhai00, Mu98].

It should be noted that most of the biochemical work was done with the rabbit muscle form of glycogenin. However, the enzyme is highly conserved within mammals.

Gene Citations: [Barbetti96]

Molecular Weight of Polypeptide: 39.253 kD (from nucleotide sequence), 38 kD (experimental) [Cao93 ]

Molecular Weight of Multimer: 38 kD (experimental) [Cao93]

Unification Links: ArrayExpress:P46976 , Mint:MINT-5000544 , ModBase:P46976 , PhosphoSite:P46976 , PhylomeDB:P46976 , Pride:P46976 , Protein Model Portal:P46976 , SMR:P46976 , String:9606.ENSP00000340736 , Swiss-Model:P46976 , UniProt:P46976

Relationship Links: CAZy:IN-FAMILY:GT8 , Entrez-Nucleotide:PART-OF:U44131 , InterPro:IN-FAMILY:IPR002495 , PDB:Structure:3Q4S , PDB:Structure:3QVB , PDB:Structure:3RMV , PDB:Structure:3RMW , PDB:Structure:3T7M , PDB:Structure:3T7N , PDB:Structure:3T7O , PDB:Structure:3U2T , PDB:Structure:3U2U , PDB:Structure:3U2V , PDB:Structure:3U2W , PDB:Structure:3U2X , Pfam:IN-FAMILY:PF01501

Reactions known to consume the compound:

glycogen biosynthesis II (from UDP-D-Glucose) :
UDP-α-D-glucose[out] + a glycogenin[out] → a glucosyl-glycogenin[out] + UDP[out] + H+[out]

Gene-Reaction Schematic: ?


Enzymatic reaction of: UDP-α-D-glucose:glycogenin α-D-glucosyltransferase (glycogenin 1)

EC Number: 2.4.1.186

UDP-α-D-glucose[out] + a glycogenin[out] <=> a glucosyl-glycogenin[out] + UDP[out] + H+[out]

The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the Enzyme Commission system.

The reaction is favored in the direction shown.

In Pathways: glycogen biosynthesis II (from UDP-D-Glucose)

Cofactors or Prosthetic Groups: Mn2+ [Whelan86]

Inhibitors (Unknown Mechanism): maltose [Cao93] , UDP [Cao93] , UTP [Cao93]


Enzymatic reaction of: UDP-α-D-glucose:glucosyl-glycogenin α-D-glucosyltransferase (glycogenin 1)

EC Number: 2.4.1.186

In Pathways: glycogen biosynthesis II (from UDP-D-Glucose)

Cofactors or Prosthetic Groups: Mn2+ [Whelan86]

Inhibitors (Unknown Mechanism): UDP [Cao93] , UTP [Cao93] , maltose [Cao93]

Kinetic Parameters:

Substrate
Km (μM)
Citations
UDP-α-D-glucose
4.5
[Cao93]

pH(opt): 8 [Cao93]


References

Barbetti96: Barbetti F, Rocchi M, Bossolasco M, Cordera R, Sbraccia P, Finelli P, Consalez GG (1996). "The human skeletal muscle glycogenin gene: cDNA, tissue expression and chromosomal localization." Biochem Biophys Res Commun 220(1);72-7. PMID: 8602861

Cao93: Cao Y, Mahrenholz AM, DePaoli-Roach AA, Roach PJ (1993). "Characterization of rabbit skeletal muscle glycogenin. Tyrosine 194 is essential for function." J Biol Chem 268(20);14687-93. PMID: 8325847

Lomako04: Lomako J, Lomako WM, Whelan WJ (2004). "Glycogenin: the primer for mammalian and yeast glycogen synthesis." Biochim Biophys Acta 1673(1-2);45-55. PMID: 15238248

Mu97: Mu J, Skurat AV, Roach PJ (1997). "Glycogenin-2, a novel self-glucosylating protein involved in liver glycogen biosynthesis." J Biol Chem 272(44);27589-97. PMID: 9346895

Mu98: Mu J, Roach PJ (1998). "Characterization of human glycogenin-2, a self-glucosylating initiator of liver glycogen metabolism." J Biol Chem 273(52);34850-6. PMID: 9857012

Whelan86: Whelan WJ (1986). "The initiation of glycogen synthesis." Bioessays 5(3);136-40. PMID: 3105529

Zhai00: Zhai L, Mu J, Zong H, DePaoli-Roach AA, Roach PJ (2000). "Structure and chromosomal localization of the human glycogenin-2 gene GYG2." Gene 242(1-2);229-35. PMID: 10721716


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 18.5 on Sat Dec 20, 2014, biocyc11.