Glycogen metabolism (WP835)

Gallus gallus

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].


Alex Pico , Christine Chichester , Egon Willighagen , Martina Summer-Kutmon , and Eric Weitz


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Gallus gallus



Pathway Ontology

glycogen metabolic pathway


Label Type Compact Identifier Comment
cAMP Metabolite hmdb:HMDB0000058
UDP-glucose Metabolite hmdb:HMDB0000286
Glucose 1-phosphate Metabolite hmdb:HMDB0001586
PPP2CB GeneProduct ncbigene:396021
PHKB GeneProduct ncbigene:415741
GYS2 GeneProduct ncbigene:418201
PPP2R5C GeneProduct ncbigene:423460
CALM1 GeneProduct ncbigene:396523
PHKA1 GeneProduct ncbigene:422181
PPP2R2C GeneProduct ncbigene:422858
RCJMB04_2f16 GeneProduct ncbigene:421248
UGP2 GeneProduct ncbigene:373900
GYS1 GeneProduct ncbigene:378934
PPP2R3A GeneProduct ncbigene:424733
GYG1 GeneProduct ncbigene:425050
CALM3 GeneProduct ncbigene:416692
PPP2R5E GeneProduct ncbigene:423512
PPP2CA GeneProduct ncbigene:416318
UGP2 GeneProduct ncbigene:373900
GYG2 GeneProduct ncbigene:418660
PPP2R5D GeneProduct ncbigene:421250
PPP2R2B GeneProduct ncbigene:416350
AGL GeneProduct ncbigene:424474
PPP2R5A GeneProduct ncbigene:421372
PPP2R3B GeneProduct ncbigene:418670
PHKA2 GeneProduct ncbigene:418612
RCJMB04_5f2 GeneProduct ncbigene:419523
GSK3B GeneProduct ncbigene:418335
PHKG1 GeneProduct ncbigene:417543
PPP2R1B GeneProduct ncbigene:777130
GBE1 GeneProduct ncbigene:427964
PGM1 GeneProduct ncbigene:424691
PPP2R4 GeneProduct ncbigene:426329
PYGL GeneProduct ncbigene:378909