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Glycogen

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Glycogen Glycogen Synthesis Glycogen Synthase 1-4 bonds Summary Skeletal Muscle Epi/N-Epi (beta receptor) C-AMP Ca++ (actives phosphorylase kinase These will ... – PowerPoint PPT presentation

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Title: Glycogen


1
Glycogen
2

Human liver - 50 g/kg wet wt.

Skeletal muscle - 15 g/kg wet wt.
Glycogenin protein core Glycosome
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  • ? 1-4 bonds
  • 1-6 bonds
  • Glycoside bonds

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Tier 8
Proglycogen (acid insoluble) Macroglycogen (acid
soluble)
Size glycogenin Proglycogen
Macroglycogen 12 tiers is the maximum branches
too dense to allow GS
7
Two Forms of Muscle Glycogen
Proglycogen
Macroglycogen
Glygogenin
Lomako, et al., FASAB J. 9, 1126-1137, 1995
75 proglycogen/25 macroglycogen
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Glycogen SynthesisGlycogen Synthase ?1-4 bonds
Glycosyl 46 transferase Branching enzyme
(at least 11)
(move at least 7)
( leave at least 4)
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Glycogenolysis
1-4 Bond
1-6 Bond
(Glucose-1-P
Glucose-6-P)
(phosphoglucomutase)
phosphorylase
Glucose -6-P
a
b
c
f
e
d
a
b
c
glycosyl 44 transferase
(breaks a 1-4, makes a 1-4)
to glycolysis
(NEXT)
15
Glycogenolysis (cont.)
a
b
c
f
e
d
a
b
c
glycosyl 44 transferase
a
b
c
f
e
d
to another chain
a
b
c
Amylo 16 glucosidase
free glucose
free glucose
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Summary
Glycogenolysis- the break down of glycogen into
glucose
Glycogen Synthesis- the storage of glucose via
glycogen formation -Glycogen Synthase- enzyme
responsible for making ? 1-4 bonds between
glucose molecules -Glycosyl 46 transferase-
enzyme that breaks ? 1-4 bonds, and makes ? 1-6
bonds to allow for branching
25
Summary
  • Skeletal Muscle
  • Epi/N-Epi (beta receptor)
  • ? C-AMP
  • ? Ca (actives phosphorylase kinase
  • These will increase activity of phosphorylase and
    decrease glycogen synthase
  • Insulin
  • ? PDE activity which will decrease C-AMP
  • ? PP-1 which will increase the activity of GS and
    decrease the activity of phosphorylase

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HOW CAN WE AVOID THIS EVENT?
28
VERY GENERALIZED SCHEME of SUBSTRATE USE vs TIME
Reliance on fats
Liver depleting
Muscle depleting
29
Three CHO-Loading Protocols Two Depletion One
Taper
Saltin and Hermansen, Nut. Physical Activity,
pp.32-46, 1967
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Phosphorylates glycogen synthase
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CA actives Phosphorylase Kinase at the start of
exercise by 20x. Ca binds to gamma subunit of
PK. Phosphorylase Kinase activated via C-AMP and
PKA. Phosphorylase kinase phosphorylates
Phosphorylase at serine 14. AMP allosterically
actives Phosphorylase.
34
Inactive
Active
- P
Insulin activates PP-1 and PDE (phosphodiesterase)
. This will decrease C-AMP and dephosphorylate
proteins that were phosphorylated by PKA
35
Order of Glycogen Resynthesis
Lomako, et. al.,FASAB 71386-1393
36
Glycogen Storage Diseases
  • Type I Von Gierke Disease Glucose-6-phosphatas
    e Defect
  • Hypoglycemia occurs due to defect of the final
    step of gluconeogenesis.
  • This disease, affects only liver and renal
    tubule cells
  • Decreased mobilization of glycogen produces
    hepatomegaly.
  • Type V McArdle Disease Skeletal Muscle
    Glycogen Phosphorylase Defect
  • Skeletal muscle is affected, whereas the liver
    enzyme is normal.
  • Exercise capacity is greatly reduced,
    hypoglycemia during exercise
  • There is no rise in blood lactate during
    strenuous exercise.
  • Muscle contains a high level of glycogen with
    normal structure
  • Type VI Hers Disease Liver Glycogen
    Phosphorylase Defect
  • Liver is affected, whereas the skeletal muscle
    enzyme is normal.
  • Marked hepatomegaly occurs due to a high level
    of glycogen with normal structure..
  • Following administration of glucagon, there is
    no increase in blood glucose.

37
Slow Phase- dependent on insulin concentration
Rapid Phase increased insulin sensitivity
GLUT 4 from exercise
Casey, et al., J.Physiol. 48(1) 265-271, 1995.
38
EFFECT of DETRAINING on MUSCLE GLYCOGEN
CONCENTRATIONS
60
80
72
100
Costill, et., al., Med. Sci. Sports Exerc.,
17(3)339-343, 1985.
39
Muscle Glycogen During 3 days of Endurance
Training and al Low-CHO vs High-CHO Diet
Costill, et. al., J.A.P. 31(6) 834-838, 1971.
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