Glycogen synthesis and degradation (WP500)

Homo sapiens

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]. Proteins on this pathway have targeted assays available via the [ CPTAC Assay Portal]


Kdahlquist , Kristina Hanspers , Andra Waagmeester , Susan Coort , Alex Pico , Harm Nijveen , Martina Summer-Kutmon , Denise Slenter , Jesse Vercoulen , Friederike Ehrhart , Egon Willighagen , Eric Weitz , and Finterly Hu


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Homo sapiens



Pathway Ontology

glycogen metabolic pathway glycogen degradation pathway


Label Type Compact URI Comment
Glycogen Metabolite cas:9005-79-2
cAMP Metabolite hmdb:HMDB0000058
Glycogen (n+1) Metabolite cas:9005-79-2
Glucose-1-phosphate Metabolite cas:59-56-3
UDP-glucose Metabolite hmdb:HMDB0000286
Glucose 1-phosphate Metabolite hmdb:HMDB0001586
Glycogen Metabolite cas:9005-79-2
D-Glucose Metabolite hmdb:HMDB0000122
Glycogen (n+1) Metabolite cas:9005-79-2
Glucose-6-phosphate (2-) Metabolite chebi:75052
PYGM GeneProduct ncbigene:5837
PPP2CB GeneProduct ncbigene:5516
PHKB GeneProduct ncbigene:5257
GYS2 GeneProduct ncbigene:2998
PPP2R5B GeneProduct ncbigene:5526
PHKG2 GeneProduct ncbigene:5261
PPP2R5C GeneProduct ncbigene:5527
CALM1 GeneProduct ncbigene:801
PHKA1 GeneProduct ncbigene:5255
PPP2R2C GeneProduct ncbigene:5522
PYGB GeneProduct ncbigene:5834
UGP2 GeneProduct ncbigene:7360
GYS1 GeneProduct ncbigene:2997
GSK3A GeneProduct ncbigene:2931
PPP2R3A GeneProduct ncbigene:5523
GYG GeneProduct ncbigene:2992
PPP2R1A GeneProduct ncbigene:5518
CALM3 GeneProduct ncbigene:808
PPP2R5E GeneProduct ncbigene:5529
PPP2CA GeneProduct ncbigene:5515
UGP2 GeneProduct ncbigene:7360
GYG2 GeneProduct ncbigene:8908
PPP2R5D GeneProduct ncbigene:5528
PPP2R2B GeneProduct ncbigene:5521
AGL GeneProduct ncbigene:178
PPP2R5A GeneProduct ncbigene:5525
CALM2 GeneProduct ncbigene:805
PPP2R3B GeneProduct ncbigene:28227
PHKA2 GeneProduct ncbigene:5256
PPP2R2A GeneProduct ncbigene:5520
GSK3B GeneProduct ncbigene:2932
PHKG1 GeneProduct ncbigene:5260
PPP2R1B GeneProduct ncbigene:5519
GBE1 GeneProduct ncbigene:2632
PGM1 GeneProduct ncbigene:5236
PPP2R4 GeneProduct ncbigene:5524
PYGL GeneProduct ncbigene:5836
PYG GeneProduct eccode: glycogen phosphorylase
hexokinase GeneProduct eccode: glycogen phosphorylase
PYG, muscle form Protein uniprot:P11217
Putative hexokinase HKDC1 Protein uniprot:Q2TB90 expression pharynx, thymus, colon, esophagus, and eye tissue
PYG, liver form Protein uniprot:P06737
PYG, brain form Protein uniprot:P11216
Hexokinase-1 (Brain) Protein uniprot:P19367
Hexokinase-2 (muscle) Protein uniprot:P52789
Hexokinase-3 Protein uniprot:P52790 predominant hexokinase in myeloid cells, particularly granulocytes


  1. Metabolism at a Glance [Internet]. Salway JG. John Wiley & Sons; 2017. 147 p. Available from: OpenLibrary Worldcat
  2. Glycogen metabolism in the normal red blood cell. Moses SW, Bashan N, Gutman A. Blood. 1972 Dec;40(6):836–43. PubMed Europe PMC Scholia