Glycogen metabolism
- Created by: jessica
- Created on: 12-12-12 10:11
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- Glycogen metabolism
- Synthesis needs Uridine Diphosphate Glucose (UDP-glucose)
- UDP-glucose made by reaction of UTP and glucose-1-phosphate
- Irreversible hydrolysis of pyrophosphate drives UDP-glucose synthesis
- Glucose-1-phosphate + UTP = UDP-glucose + PPi (reversible reaction) PPi + H2O=2Pi
- Glucose-1-phosphate + UTP+ H2O=UDP-glucose + 2Pi
- Irreversible hydrolysis of pyrophosphate drives UDP-glucose synthesis
- Glycogenin is the primer for glycogen synthesis
- UDP-glucose made by reaction of UTP and glucose-1-phosphate
- Glucose residues linked by 1-4 glycosidic bonds
- Every 10 residues, branches by 1-6 glycosidic bonds
- Glucose-6-phosphate from glycogen has 3 fates
- 3:processed by pentose phosphate pathway to yield NADPH and ribose derivatives
- 1:initial substrate for glycolysis
- 2:converted into free glucose for release into bloodstream
- Glycogen molecule has 12 layers of glucose molecules
- Synthesis equation
- Glycogen(n) + UDP-glucose = Glycogen(n) + 1 + UDP
- Degradation has 3 steps
- 2:remodelling glycogen substrate for more degradation
- Transferase and alpha 1-6 glucosidase remodel
- 1:release of glucose-1-phosphate from glycogen
- Glycogen (n residues) + Pi = Glucose-1-phosphate + Glycogen (n-1 residue) (reversible reaction)
- Orthophosphate splits linkage between C1 of terminal residue and C4 of adjacent residue
- Phosphogluco-mutase converts glucose-1-phosphate to glucose-6-phosphate
- Glycogen (n residues) + Pi = Glucose-1-phosphate + Glycogen (n-1 residue) (reversible reaction)
- 3:conversion of glucose-1-phosphate into glucose-6-phosphate for further metabolism
- 2:remodelling glycogen substrate for more degradation
- Degradation Equation
- Glycogen(n) + 1+Pi=Glycogen(n) + Glucose-1-phosphate
- Branching
- increases solubility and synthesis/ degradation rate
- insulin stimulates synthesis
- inactivates glycogen synthase and activates protein kinases
- Synthesis needs Uridine Diphosphate Glucose (UDP-glucose)
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