Glycogen Synthesis and Degradation (Homo sapiens)

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321DegradationSer/Thr protein phosphatase 2ASynthesisPhosphorylase KinaseDifferent formsPPP2CBPPP2R3BPYGMGlycogen (n+1)GYG2PPP2R2BPYG, brain formUGP2PPP2R5EPPP2R2AGlycogenPPP2R5AGlucose-1-phosphateD-GlucosePHKA1PPP2R4PHKG2CALM2PPP2R5BGYS1AGLPPP2R2CPHKG1UGP2Hexokinase-1 (Brain)PPP2R5DGlucose 1-phosphatePPP2R1APPP2R5CPPP2CAGlucose-6-phosphate (2-)Putative hexokinase HKDC1CALM3GSK3BPGM1cAMPCALM1UDP-glucosePYGBPYG, liver formGBE1PPP2R3APYGLGlycolysisGlycogenGYS2PHKBGlycogen (n+1)PYG, muscle formGSK3APPP2R1BPHKA2GYGPYGhexokinaseHexokinase-2 (muscle)Hexokinase-3 Different forms


Glycogen is a very large, branched polymer of glucose residues. Within skeletal muscle and liver glucose is stored as glycogen. In the liver, glycogen synthesis and degradation are regulated to maintain blood-glucose levels as required to meet the needs of the organism as a whole. In contrast, in muscle, these processes are regulated to meet the energy needs of the muscle itself.

Glycogen synthesis is, unlike its breakdown, endergonic. This means that glycogen synthesis requires the input of energy. Energy for glycogen synthesis comes from UTP, which reacts with glucose-1-phosphate, forming UDP-glucose, in reaction catalyzed by UDP-glucose pyrophosphorylase. Glycogen is synthesized from monomers of UDP-glucose by the enzyme glycogen synthase, which progressively lengthens the glycogen chain with (a1->4) bonded glucose. As glycogen synthase can only lengthen an existing chain, the protein glycogenin is needed to initiate the synthesis of glycogen. The glycogen-branching enzyme, amylo (a1->4) to (a1->6) transglycosylase, catalyzes the transfer of a terminal fragment of 6-7 glucose residues from a nonreducing end to the C-6 hydroxyl group of a glucose residue deeper into the interior of the glycogen molecule. The branching enzyme can act upon only a branch having at least 11 residues, and the enzyme may transfer to the same glucose chain or adjacent glucose chains.

Glycogen degradation consists of three steps: (1) the release of glucose 1-phosphate from glycogen, (2) the remodeling of the glycogen substrate to permit further degradation, and (3) the conversion of glucose 1-phosphate into glucose 6-phosphate for further metabolism.

Information partly derived from "Biochemistry" by Stryer and Wikipedia.

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Ontology Terms



  1. Salway, Jack G; ''Metabolism at a Glance''; , 2016
  2. Salway, Jack G; ''Metabolism at a Glance''; , 2016
  3. Moses SW, Bashan N, Gutman A; ''Glycogen metabolism in the normal red blood cell.''; Blood, 1972 PubMed Europe PMC


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102318view08:02, 20 December 2018FehrhartChanged title due to overlap with Reactome pathway
97542view14:38, 24 May 2018Jessev1993Added annotated nodes for different forms of hexokinase and PYG
94085view12:36, 18 August 2017DeSlOntology Term : 'glycogen degradation pathway' added !
94084view12:35, 18 August 2017DeSlConnected last line.
93721view13:40, 14 August 2017DeSlChanged IDs for open-forms of several glucoses to closed forms; added glycogen to gluco-6-phos conversion+inhibition by glucose
89807view11:45, 6 October 2016Mkutmonfix description
63201view20:54, 8 May 2013MaintBotUpdating gpml version
45329view20:15, 7 October 2011AlexanderPicoModified description
45324view20:11, 7 October 2011AlexanderPicoOntology Term : 'glycogen metabolic pathway' added !
43019view11:51, 28 May 2011HarmNijveencorrected CAS ID for glucose-6-phospate
41230view23:46, 1 March 2011MaintBotRemoved redundant pathway information and comments
38907view20:41, 24 September 2010AlexanderPico
38906view20:40, 24 September 2010AlexanderPicopathway node, catalysis edges and layout
35631view19:04, 12 February 2010SusanModified description
35630view19:00, 12 February 2010SusanPeriodical save, work in progress
35452view11:48, 12 February 2010Andraadded reference
34475view18:35, 10 December 2009MaintBotAutomatic update of empty xrefs
32124view13:53, 14 August 2009MaintBotFixed group labels
21730view11:32, 14 November 2008MaintBot[[Pathway:Homo sapiens:Glycogen Metabolism]] moved to [[Pathway:WP500]]: Moved to stable identifier
14700view21:06, 23 May 2008KhanspersAdded connectors and metabolites
14697view19:41, 23 May 2008Khanspersconnectors
13072view11:13, 17 May 2008MaintBotautomated metabolite conversion
8090view13:46, 7 January 2008MaintBot[[Pathway:Human:Glycogen Metabolism]] moved to [[Pathway:Homo sapiens:Glycogen Metabolism]]: Renaming species
7667view16:08, 18 December 2007MaintBotfixed category names
7366view12:42, 4 November 2007MaintBotAdded categories to GPML
6328view22:17, 22 May 2007Kdahlquistgpml file for [[Human:Glycogen_Metabolism]]

External references


View all...
NameTypeDatabase referenceComment
AGLGeneProduct178 (Entrez Gene)
CALM1GeneProduct801 (Entrez Gene)
CALM2GeneProduct805 (Entrez Gene)
CALM3GeneProduct808 (Entrez Gene)
D-GlucoseMetaboliteHMDB00122 (HMDB)
GBE1GeneProduct2632 (Entrez Gene)
GSK3AGeneProduct2931 (Entrez Gene)
GSK3BGeneProduct2932 (Entrez Gene)
GYG2GeneProduct8908 (Entrez Gene)
GYGGeneProduct2992 (Entrez Gene)
GYS1GeneProduct2997 (Entrez Gene)
GYS2GeneProduct2998 (Entrez Gene)
Glucose 1-phosphateMetaboliteHMDB01586 (HMDB)
Glucose-1-phosphateMetabolite59-56-3 (CAS)
Glucose-6-phosphate (2-)MetaboliteCHEBI:75052 (ChEBI)
Glycogen (n+1)Metabolite9005-79-2 (CAS)
GlycogenMetabolite9005-79-2 (CAS)
GlycolysisPathwayWP534 (WikiPathways)
Hexokinase-1 (Brain)ProteinP19367 (Uniprot-TrEMBL)
Hexokinase-2 (muscle)ProteinP52789 (Uniprot-TrEMBL)
Hexokinase-3 ProteinP52790 (Uniprot-TrEMBL) predominant hexokinase in myeloid cells, particularly granulocytes
PGM1GeneProduct5236 (Entrez Gene)
PHKA1GeneProduct5255 (Entrez Gene)
PHKA2GeneProduct5256 (Entrez Gene)
PHKBGeneProduct5257 (Entrez Gene)
PHKG1GeneProduct5260 (Entrez Gene)
PHKG2GeneProduct5261 (Entrez Gene)
PPP2CAGeneProduct5515 (Entrez Gene)
PPP2CBGeneProduct5516 (Entrez Gene)
PPP2R1AGeneProduct5518 (Entrez Gene)
PPP2R1BGeneProduct5519 (Entrez Gene)
PPP2R2AGeneProduct5520 (Entrez Gene)
PPP2R2BGeneProduct5521 (Entrez Gene)
PPP2R2CGeneProduct5522 (Entrez Gene)
PPP2R3AGeneProduct5523 (Entrez Gene)
PPP2R3BGeneProduct28227 (Entrez Gene)
PPP2R4GeneProduct5524 (Entrez Gene)
PPP2R5AGeneProduct5525 (Entrez Gene)
PPP2R5BGeneProduct5526 (Entrez Gene)
PPP2R5CGeneProduct5527 (Entrez Gene)
PPP2R5DGeneProduct5528 (Entrez Gene)
PPP2R5EGeneProduct5529 (Entrez Gene)
PYG, brain formProteinP11216 (Uniprot-TrEMBL)
PYG, liver formProteinP06737 (Uniprot-TrEMBL)
PYG, muscle formProteinP11217 (Uniprot-TrEMBL)
PYGGeneProduct2.4.1.1 (Enzyme Nomenclature) glycogen phosphorylase
PYGBGeneProduct5834 (Entrez Gene)
PYGLGeneProduct5836 (Entrez Gene)
PYGMGeneProduct5837 (Entrez Gene)
Putative hexokinase HKDC1ProteinQ2TB90 (Uniprot-TrEMBL) expression pharynx, thymus, colon, esophagus, and eye tissue
UDP-glucoseMetaboliteHMDB00286 (HMDB)
UGP2GeneProduct7360 (Entrez Gene)
cAMPMetaboliteHMDB00058 (HMDB)
hexokinaseGeneProduct2.7.1.1 (Enzyme Nomenclature) glycogen phosphorylase

Annotated Interactions

No annotated interactions

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