Glycogenin is an enzyme involved in converting glucose to glycogen. It acts as a primer, by polymerizing the first few glucose molecules, after which other enzymes take over. It is a homodimer of 37-kDa subunits and is classified as a glycosyltransferase.
This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. The systematic name of this enzyme class is UDP-alpha-D-glucose:glycogenin alpha-D-glucosyltransferase. Other names in common use include:
glycogenin,
priming glucosyltransferase, and
UDP-glucose:glycogenin glucosyltransferase.
One may also notice that the naming of glycogenin hints at its function, with the glyco prefix referring to a carbohydrate and the genin suffix derived from the Latin genesis meaning novel, source, or beginning. This hints at the role of glycogenin to simply start glycogen synthesis before glycogen synthase takes over.
The main enzyme involved in glycogen polymerisation, glycogen synthase in the liver and in the muscle glycogen synthesis is initiated by UDP-Glucose, can only add to an existing chain of at least 3 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.
Structureedit
2-D cross-sectional view of glycogen. A core protein of glycogenin is surrounded by branches of glucose units. The entire globular complex may contain approximately 30 000 glucose units.[5]
Isozymesedit
In humans, there are two isoforms of glycogenin — glycogenin-1, encoded by GYG1, and expressed in muscle; and glycogenin-2, encoded by GYG2, and expressed in the liver and cardiac muscle, but not skeletal muscle. Patients have been found with defective GYG1, resulting in muscle cells with the inability to store glycogen, and consequential weakness and heart disease.[6]
^PDB: 1LL3; Gibbons BJ, Roach PJ, Hurley TD (May 2002). "Crystal structure of the autocatalytic initiator of glycogen biosynthesis, glycogenin". J. Mol. Biol. 319 (2): 463–77. doi:10.1016/S0022-2836(02)00305-4. PMID 12051921.
^Barengo R, Krisman CR (May 1978). "Initiation of glycogen biosynthesis in Escherichia coli. Studies of the properties of the enzymes involved". Biochimica et Biophysica Acta (BBA) - General Subjects. 540 (2): 190–6. doi:10.1016/0304-4165(78)90131-9. PMID 418819.
^Butler NA, Lee EY, Whelan WJ (May 1977). "A protein-bound glycogen component of rat liver". Carbohydrate Research. 55: 73–82. doi:10.1016/s0008-6215(00)84444-4. PMID 861979.
^Whelan WJ (September 1998). "Pride and prejudice: the discovery of the primer for glycogen synthesis". Protein Sci. 7 (9): 2038–41. doi:10.1002/pro.5560070921. PMC2144155. PMID 9761486.
^Katch, Victor L.; McArdle, William D.; Katch, Frank I. (2007). Exercise physiology: energy, nutrition, and human performance. Philadelphia: Lippincott Williams and Wilkins. p. 12. ISBN978-0-7817-4990-9.
^Moslemi AR, Lindberg C, Nilsson J, Tajsharghi H, Andersson B, Oldfors A (April 2010). "Glycogenin-1 deficiency and inactivated priming of glycogen synthesis". N. Engl. J. Med. 362 (13): 1203–10. doi:10.1056/NEJMoa0900661. PMID 20357282.
Further readingedit
Krisman CR, Barengo R (1975). "A precursor of glycogen biosynthesis: alpha-1,4-glucan-protein". Eur. J. Biochem. 52 (1): 117–23. doi:10.1111/j.1432-1033.1975.tb03979.x. PMID 809265.
Pitcher J, Smythe C, Campbell DG, Cohen P (1987). "Identification of the 38-kDa subunit of rabbit skeletal muscle glycogen synthase as glycogenin". Eur. J. Biochem. 169 (3): 497–502. doi:10.1111/j.1432-1033.1987.tb13637.x. PMID 3121316.
Pitcher J, Smythe C, Cohen P (1988). "Glycogenin is the priming glucosyltransferase required for the initiation of glycogen biogenesis in rabbit skeletal muscle". Eur. J. Biochem. 176 (2): 391–5. doi:10.1111/j.1432-1033.1988.tb14294.x. PMID 2970965.
Berman, M.C. and Opie, L.A. (Eds.), Membranes and Muscle, ICSU Press/IRL Press, Oxford, 1985, p. 65-84.
Rodriguez IR, Whelan WJ (1985). "A novel glycosyl-amino acid linkage: rabbit-muscle glycogen is covalently linked to a protein via tyrosine". Biochem. Biophys. Res. Commun. 132 (2): 829–36. doi:10.1016/0006-291X(85)91206-9. PMID 4062948.
Lomako J, Lomako WM, Whelan WJ (1988). "A self-glucosylating protein is the primer for rabbit muscle glycogen biosynthesis". FASEB J. 2 (15): 3097–103. doi:10.1096/fasebj.2.15.2973423. PMID 2973423. S2CID 24083688.
Alonso MD, Lomako J, Lomako WM, Whelan WJ (1995). "Catalytic activities of glycogenin additional to autocatalytic self-glucosylation". J. Biol. Chem. 270 (25): 15315–9. doi:10.1074/jbc.270.25.15315. PMID 7797519.
Alonso MD, Lomako J, Lomako WM, Whelan WJ (1995). "A new look at the biogenesis of glycogen". FASEB J. 9 (12): 1126–37. doi:10.1096/fasebj.9.12.7672505. PMID 7672505. S2CID 40281321.
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. doi:10.1074/jbc.273.52.34850. PMID 9857012.
External linksedit
Wikimedia Commons has media related to Glycogenin.
glycogenin, enzyme, involved, converting, glucose, glycogen, acts, primer, polymerizing, first, glucose, molecules, after, which, other, enzymes, take, over, homodimer, subunits, classified, glycosyltransferase, glycogenin, glucosyltransferase, structure, from. Glycogenin is an enzyme involved in converting glucose to glycogen It acts as a primer by polymerizing the first few glucose molecules after which other enzymes take over It is a homodimer of 37 kDa subunits and is classified as a glycosyltransferase glycogenin glucosyltransferaseGlycogenin structure from rabbit 1 IdentifiersEC no 2 4 1 186CAS no 117590 73 5DatabasesIntEnzIntEnz viewBRENDABRENDA entryExPASyNiceZyme viewKEGGKEGG entryMetaCycmetabolic pathwayPRIAMprofilePDB structuresRCSB PDB PDBe PDBsumSearchPMCarticlesPubMedarticlesNCBIproteinsIt catalyzes the chemical reactions UDP alpha D glucose glycogenin UDP alpha D glucosylglycogenin UDP alpha D glucose a glucosyl glycogenin 1 4 alpha D glucosyl n glucosyl glucogenin UDP H Thus the two substrates of this enzyme are UDP alpha D glucose and glycogenin whereas its two products are UDP and alpha D glucosylglycogenin 2 3 Contents 1 Nomenclature 2 Discovery 3 Function 4 Structure 5 Isozymes 6 References 7 Further reading 8 External linksNomenclature editThis enzyme belongs to the family of glycosyltransferases specifically the hexosyltransferases The systematic name of this enzyme class is UDP alpha D glucose glycogenin alpha D glucosyltransferase Other names in common use include glycogenin priming glucosyltransferase and UDP glucose glycogenin glucosyltransferase One may also notice that the naming of glycogenin hints at its function with the glyco prefix referring to a carbohydrate and the genin suffix derived from the Latin genesis meaning novel source or beginning This hints at the role of glycogenin to simply start glycogen synthesis before glycogen synthase takes over Discovery editGlycogenin was discovered in 1984 by Dr William J Whelan a fellow of the Royal Society of London and former professor of Biochemistry at the University of Miami 4 Function editThe main enzyme involved in glycogen polymerisation glycogen synthase in the liver and in the muscle glycogen synthesis is initiated by UDP Glucose can only add to an existing chain of at least 3 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 Structure edit nbsp 2 D cross sectional view of glycogen A core protein of glycogenin is surrounded by branches of glucose units The entire globular complex may contain approximately 30 000 glucose units 5 Isozymes editIn humans there are two isoforms of glycogenin glycogenin 1 encoded by GYG1 and expressed in muscle and glycogenin 2 encoded by GYG2 and expressed in the liver and cardiac muscle but not skeletal muscle Patients have been found with defective GYG1 resulting in muscle cells with the inability to store glycogen and consequential weakness and heart disease 6 glycogenin 1IdentifiersSymbolGYG1Alt symbolsGYGNCBI gene2992HGNC4699OMIM603942RefSeqNM 004130UniProtP46976Other dataEC number2 4 1 186LocusChr 3 q24 q25 1Search forStructuresSwiss modelDomainsInterPro glycogenin 2IdentifiersSymbolGYG2NCBI gene8908HGNC4700OMIM300198RefSeqNM 003918UniProtO15488Other dataEC number2 4 1 186LocusChr X p22 3Search forStructuresSwiss modelDomainsInterProReferences edit PDB 1LL3 Gibbons BJ Roach PJ Hurley TD May 2002 Crystal structure of the autocatalytic initiator of glycogen biosynthesis glycogenin J Mol Biol 319 2 463 77 doi 10 1016 S0022 2836 02 00305 4 PMID 12051921 Barengo R Krisman CR May 1978 Initiation of glycogen biosynthesis in Escherichia coli Studies of the properties of the enzymes involved Biochimica et Biophysica Acta BBA General Subjects 540 2 190 6 doi 10 1016 0304 4165 78 90131 9 PMID 418819 Butler NA Lee EY Whelan WJ May 1977 A protein bound glycogen component of rat liver Carbohydrate Research 55 73 82 doi 10 1016 s0008 6215 00 84444 4 PMID 861979 Whelan WJ September 1998 Pride and prejudice the discovery of the primer for glycogen synthesis Protein Sci 7 9 2038 41 doi 10 1002 pro 5560070921 PMC 2144155 PMID 9761486 Katch Victor L McArdle William D Katch Frank I 2007 Exercise physiology energy nutrition and human performance Philadelphia Lippincott Williams and Wilkins p 12 ISBN 978 0 7817 4990 9 Moslemi AR Lindberg C Nilsson J Tajsharghi H Andersson B Oldfors A April 2010 Glycogenin 1 deficiency and inactivated priming of glycogen synthesis N Engl J Med 362 13 1203 10 doi 10 1056 NEJMoa0900661 PMID 20357282 Further reading editKrisman CR Barengo R 1975 A precursor of glycogen biosynthesis alpha 1 4 glucan protein Eur J Biochem 52 1 117 23 doi 10 1111 j 1432 1033 1975 tb03979 x PMID 809265 Pitcher J Smythe C Campbell DG Cohen P 1987 Identification of the 38 kDa subunit of rabbit skeletal muscle glycogen synthase as glycogenin Eur J Biochem 169 3 497 502 doi 10 1111 j 1432 1033 1987 tb13637 x PMID 3121316 Pitcher J Smythe C Cohen P 1988 Glycogenin is the priming glucosyltransferase required for the initiation of glycogen biogenesis in rabbit skeletal muscle Eur J Biochem 176 2 391 5 doi 10 1111 j 1432 1033 1988 tb14294 x PMID 2970965 Berman M C and Opie L A Eds Membranes and Muscle ICSU Press IRL Press Oxford 1985 p 65 84 Rodriguez IR Whelan WJ 1985 A novel glycosyl amino acid linkage rabbit muscle glycogen is covalently linked to a protein via tyrosine Biochem Biophys Res Commun 132 2 829 36 doi 10 1016 0006 291X 85 91206 9 PMID 4062948 Lomako J Lomako WM Whelan WJ 1988 A self glucosylating protein is the primer for rabbit muscle glycogen biosynthesis FASEB J 2 15 3097 103 doi 10 1096 fasebj 2 15 2973423 PMID 2973423 S2CID 24083688 Alonso MD Lomako J Lomako WM Whelan WJ 1995 Catalytic activities of glycogenin additional to autocatalytic self glucosylation J Biol Chem 270 25 15315 9 doi 10 1074 jbc 270 25 15315 PMID 7797519 Alonso MD Lomako J Lomako WM Whelan WJ 1995 A new look at the biogenesis of glycogen FASEB J 9 12 1126 37 doi 10 1096 fasebj 9 12 7672505 PMID 7672505 S2CID 40281321 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 doi 10 1074 jbc 273 52 34850 PMID 9857012 External links edit nbsp Wikimedia Commons has media related to Glycogenin glycogenin at the U S National Library of Medicine Medical Subject Headings MeSH molbio med miami edu Portal nbsp Biology Retrieved from https en wikipedia org w index php title Glycogenin amp oldid 1215536855, wikipedia, wiki, book, books, library,
