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Glycogen Metabolism. Introduction. Storage Polysaccharides. Why Polysaccharides?. Rapid mobilization Support anaerobic metabolism Animals cannot convert fats to glucose precursors. Why Polymers?. Osmotic Problem!. Glycogen Metabolism. Glycogen Breakdown. Storage Tissues.

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Presentation Transcript
why polysaccharides
Why Polysaccharides?
  • Rapid mobilization
  • Support anaerobic metabolism
  • Animals cannot convert fats to glucose precursors
why polymers

Why Polymers?

Osmotic Problem!

storage tissues
Storage Tissues
  • Liver: Glucose for bloodstream
  • Muscle: Glucose for anaerobic ATP synthesis (Glycolysis)
pathway overview
Pathway Overview
  • Structure of Glycogen
  • Glycogen Phosphorylase
  • Phosphoglucomutase
  • Glycogen Debranching Enzyme
mechanism of glycogen phosphorylase
Mechanism of Glycogen Phosphorylase

Binding Crevice Accommodates 4-5 Sugar Residues

role of pyridoxal phosphate vitamin b 6 essential cofactor
Role of Pyridoxal Phosphate(Vitamin B6 – essential cofactor)

Function: acid-base catalyst.

phosphoglucomutase3
Phosphoglucomutase

Regeneration of Glucose-1,6-bisP

thermodynamics and potential futile cycle
Thermodynamics and Potential Futile Cycle

Use hydrolysis of PPi to drive glycogen synthesis!

control of glycogen metabolism

Control of Glycogen Metabolism

Glycogen Synthase

Glycogen Phosphorylase

Why not UDP-Glucose Pyrophosphorylase?

regulatory mechanisms

Regulatory Mechanisms

Allosteric Control

Covalent Modification

allosteric control i
Allosteric Control I

EnzymeNegativePositive

Phosphorylase a (more active) Glucose

Phosphorylase b (less active) ATP G6P AMP

Gycogen Synthase a (high activity)

Glycogen Synthase b (low activity) ADP Pi G6P

advantages of covalent modification
Advantages of Covalent Modification
  • Sensitivity to more allosteric effectors
  • More flexibility in control patterns
  • Signal amplification
activation of phosphorylase
Activation of Phosphorylase

Signal Amplification

inactivation of phosphoprotein phosphatase i
Inactivation of Phosphoprotein Phosphatase I

Importance of Protein-Protein Interactions

integration of glycogen metabolism control mechanisms
Integration of Glycogen Metabolism Control Mechanisms
  • Blood Glucose Levels (Liver)
    • Insulin
    • Glucagon
  • Tissue Glucose Levels (Stress)
    • Epinephrine
    • Norepinephrine
maintenance of blood glucose levels
Maintenance of Blood Glucose Levels
  • Insulin (peptide from the pancreas)
    • Produced in response to high glucose
    • Insulin-dependent glucose transporter (GLUT4)
    • cAMP decreases
  • Glucagon (peptide from the pancreas)
    • Produced in response to low glucose
    • Glucagon receptors (liver) - activation of adenylate cyclase
    • Glycogen breakdown to glucose-6-P
    • Glucose-6-phosphatase
    • Glucose enters bloodstream
response to stress muscle and other tissues
Response to Stress(Muscle and Other Tissues)
  • ß-adrenergic receptors (muscle and other tissue)
    • Activation of Adenylate Cyclase
    • Glucose-6-P for glycolysis
  • Stimulates pancreatic cells to produce glucagon