G-6-PglucoseF-6-PF-1,6-bisPG-3-PDHAP1,3,bis-PGPEP2-P-GPyruvate3-P-G

OAApyruvatePEPpyruvateAspmalatepyruvatelactatePEPAspOAAmalateOAApyruvatealanineglucoseG3P dehydroG3P dehydrocytosolmitochondrialmatrixfrom lactatefrom pyruvate

OAApyruvatePEPpyruvateAspmalatepyruvatelactatePEPAspOAAmalateOAApyruvatealanineglucoseG3P dehydroG3P dehydrocytosolmitochondrialmatrixPyruvate carboxylasePyruvate carboxylasetransaminasetransaminasePEPCKPEPCKfrom lactatefrom pyruvate

CelluloseStarchGlycogenb1-4 glucoseAnimals amylose amylopectin

each B-chain has two branch points all chains have the same length of 14 residues the material is distributed at 50% between A- and B-chains. a molecule of glycogenin, a protein that acts as a primer, is located at the centre of the structure.

Structure of GlycogenBBBBBBBBBBBBAAAAAAAAAAAAAAAAASee also amylopectin:fig 8-24 in Hortonamylopectin

each B-chain has two branch pointsall chains have the same length of 14 residues the material is distributed at 50% between A- and B-chains. a molecule of glycogenin, a protein that acts as a primer, is located at the centre of the structure. because synthesis and degradation takes place at non-reducing ends, branching provides more sites for these processes occur.

Structure of GlycogenBBBBBBBBBBBBAAAAAAAAAAAAAAAAASee also amylopectin:fig 8-24 in Hortonamylopectin

After a meal as much as 10% by weight of the liver may be glycogen

Regulation of glycogen synthaseAllosteric: G6PPhosphorylation : inhibits

Phosphorylase cleaves a1-4 bonds from the non-reducing termini of glycogen to yield Glucose -1-P

Glycogen debranching enzyme

Glycogen degradation: combined action of phosphorylase and debranching enzyme

branching enzymea 1 6a 1 6

Glycogen synthesis: glycogen synthase and branching enzymeUDP-glucosyltransferaseautocatalysisautocatalysisseveral cyclesglycogen synthaseseveral cyclesAmylo(1,4 1,6) transglycosylase(branching enzyme)glycogen synthase/branching enzymemultiple cyclesa1-4 linkagea1-6 linkage

Regulation of phosphorylaseAllosteric: AMP (muscle)G6P, ATPphosphorylation:

Regulation of phosphorylase: part 2Phos binactiveT

Co-ordinated regulation of phosphorylase and glycogen synthase by PKAPhos kinasebPhos kinasea-PO4GSaGSb-PO4activeactiveinactiveinactivePhosbPhosa-PO4activeinactiveCa2+See fig 13.7 Horton

GDPGDPGDPGTPGDPGTPG-protein linked receptorGb,gGaAdenylate cyclaseGTPGDPPiATPcAMP + PPi

35 cyclic AMP

Regulation of PKARRCCRCCR4 cAMPinactiveactive