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Biochem Glycogen metabolism

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Purpose of glycogen stores in:
1) Liver
2) mm
1) maintain resting glucose
2) generate ATP
Influence of insulin on transport of glucose into hepatic and extrahepatic cells?
introduction to glucose in mm cell facilitated by hexokinase which is a constitutive enzyme meaning it is not influenced by insulin. hepatic cells take up glucose by glucokinase enzyme which is an inducable enzyme (activated by insulin).
Hexokinase
Km=0.01mM
constitutive enzyme
in tissues in general
inhibited by product
Glucokinase
Km=10mM
induced enzyme
in liver
not inhibited by product (glu-6-P)
What is significance of glucose -6-Phosphate?
phosphorylating it traps it inside cell
debrancher enzyme
Glucagon world
glycogen to G1P.
debrances
glycogen phosphorylase
Glucagon world
glycogen to G1P
dephosphorylates
Glycogen synthase
Insulin world
G1P to glycogen
makes glycogen
4:6 Transferase (branching enzyme)
Insulin world
G1P to glycogen
branches for packaging in glycogen
what is glycogenin
protein that controls number of glycosyl units
Formation of Branches
2 Enzymatic activities
1) a1-4 glucosidase
2) a1-4:a1-6 transferase
Debranching
2 Enzymatic activites
1) a1-4:a1-4 transferase
2) a1-6 glucosidase
McArldle's disease
1)Enzyme
2)Organ
3)Symptoms
4) problem
1)muscle glycogen phosphorylase
2) skeletal muscle
3) weakness & cramping w/ excersize
4) can't mobilize glycogen from cell
Hers
1)Enzyme
2)Organ
3)Symptoms
4) problem
1) Liver glycogen phosphorylase
2) Liver
3) mild fasting hypoglycemia, hepatomegly
4) can't mobilize glycogen from cell
Von Gierke's
1)Enzyme
2)Organ
3)Symptoms
4) problem
1) glucose-6-phosphatase
2) Liver
3) severe hypoglycemia, hepatomegly
4) total block of glucose getting out to organism
Pompe's
1)Enzyme
2)Organ
3)Symptoms
4) problem
1) lysosomal a1-4 glucosidase
2) all organs
3) gardiomegaly; hepatomegaly
4) can't dispose of glycogen
Regulateion of glycogen synthase in
1)liver
2) skeletal mm
1)+ insulin & glucose
-glucagon & epinephrine

2) + insulin
- epinephrine
Regulateion of glycogen phosphorylase in
1)liver
2) skeletal mm
1) + epinephrine & glucagon
- insulin

2) + epinephrine, AMP, & Ca2+ (through calmodulin)

- insulin & ATP
1) Phosphorylase A
2) Phosphorylase B
1) Hormonally induced by glucagon, epinephrine, or Ca into glycogen degradation
2) Locally regulated by AMP into glycgoen regulation

Deck Info

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