Glycogen Metabolism - PowerPoint PPT Presentation

1 / 48
About This Presentation
Title:

Glycogen Metabolism

Description:

Glycogen Metabolism Introduction Storage Polysaccharides Why Polysaccharides? Rapid mobilization Support anaerobic metabolism Animals cannot convert fats to glucose ... – PowerPoint PPT presentation

Number of Views:63
Avg rating:3.0/5.0
Slides: 49
Provided by: vohChemU
Learn more at: http://voh.chem.ucla.edu
Category:

less

Transcript and Presenter's Notes

Title: Glycogen Metabolism


1
Glycogen Metabolism
  • Introduction

2
Storage Polysaccharides
3
Why Polysaccharides?
  • Rapid mobilization
  • Support anaerobic metabolism
  • Animals cannot convert fats to glucose
    precursors

4
Why Polymers?
  • Osmotic Problem!

5
Glycogen Metabolism
6
Glycogen Breakdown
7
Storage Tissues
  • Liver Glucose for bloodstream
  • Muscle Glucose for anaerobic ATP synthesis
    (Glycolysis)

8
Pathway Overview
  • Structure of Glycogen
  • Glycogen Phosphorylase
  • Phosphoglucomutase
  • Glycogen Debranching Enzyme

9
Structure of Glycogen
10
Glycogen Phosphorylasea(1 gt 4) Linkages
11
Phosphoglucomutase
12
Glycogen Debranching Enzymea(1 gt 6) Linkages
13
Reactions of Glycogen Breakdown
14
Glycogen Phosphorylase
15
Reaction of Glycogen Phosphorylase
16
Mechanism of Glycogen Phosphorylase
Binding Crevice Accommodates 4-5 Sugar Residues
17
Role of Pyridoxal Phosphate(Vitamin B6
essential cofactor)
Function acid-base catalyst.
18
Phosphoglucomutase
Reaction
19
Phosphoglucomutase
Mechanism
20
Phosphoglucomutase
Regeneration of Glucose-1,6-bisP
21
Glycogen Debranching Enzyme
22
Glycogen Synthesis
23
Phosphoglucomutase
24
Phosphoglucomutase
Mechanism
25
UDP-Glucose Pyrophosphorylase
26
Glycogen Synthase I
27
Glycogen Synthase II
28
Glycogen Branching
29
Thermodynamics and Potential Futile Cycle
Use hydrolysis of PPi to drive glycogen synthesis!
30
Control of Glycogen Metabolism
  • Glycogen Synthase
  • Glycogen Phosphorylase
  • Why not UDP-Glucose Pyrophosphorylase?

31
Regulatory Mechanisms
  • Allosteric Control
  • Covalent Modification

32
Covalent Modification I(Phosphorylase)
33
Covalent Modification II(Glycogen Synthase)
34
Allosteric Control I
Enzyme Negative Positive 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
35
Allosteric Control II
36
Advantages of Covalent Modification
  • Sensitivity to more allosteric effectors
  • More flexibility in control patterns
  • Signal amplification

37
Glycogen PhosphorylaseBicyclic Cascade
38
Formation of Cyclic AMP (cAMP)
39
Activation of Phosphorylase Kinase
40
Activation of Phosphorylase
Signal Amplification
41
Inactivation of Phosphoprotein Phosphatase I
Importance of Protein-Protein Interactions
42
Glycogen Synthase Bicyclic Cascade
43
Control of Glycogen Synthase
44
Integration of Glycogen Metabolism Control
Mechanisms
  • Blood Glucose Levels (Liver)
  • Insulin
  • Glucagon
  • Tissue Glucose Levels (Stress)
  • Epinephrine
  • Norepinephrine

45
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

46
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

47
Stress Hormones(Adrenyl Gland)
48
Glycogen Storage Diseases
Write a Comment
User Comments (0)
About PowerShow.com