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GLYCOGENOLYSIS
Presentation By Sana Zahir

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GLYCOGENOLYSIS
• Glycogen Overview:
• Homopolysaccharide
• Ready supply of glucose
• Highly branched

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Glycogen Overview (cont):

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Glycogen Overview (cont):
• 2 Glycosidic Linkages:
Linear linkage having α(14)
glycosidic bond = 90%
Branched linkage having α(16)
glycosidic bond = 10%

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Glycogen Overview (cont):
2 GLYCOSIDIC
LINKAGES

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Glycogen Overview (cont):
 Storage form of Glucose in
animals so also called as
“animal starch”
 Granular form
 High in liver (6-8%) and
muscles (1-2%)

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GLYCOGENOLYSIS:
"Degradtion Of Stored Glycogen
Producing Free Glucose And
Glucose 1 Phosphate"
Occurrence: Cytosole
Triggered by low blood glucose
levels

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GLYCOGENOLYSIS (cont):
Enzymes Involved:
1.Glycogen Phosphorylase.
2.Glycogen Debranching Enz;
3.Phosphoglucomutase.

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GLYCOGENOLYSIS (cont):
1st
Step: Phosphorolysis
Enzyme Involved: Glycogen phosphorylase
Action: Cleavage of α(1→4)linkages
Position: non-reducing ends
Product: glucose-1-phosphate
BUT
Activity of phosphorylase enzyme stops when it is 4
residue away from branched point.

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GLYCOGENOLYSIS (cont):

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GLYCOGENOLYSIS (cont):

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GLYCOGENOLYSIS (cont):
• Now Inorder To Rescue The
Process, "DEBRANCHING
ENZYME" Comes In Action

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GLYCOGENOLYSIS (cont):
• 2nd
Step: Removal of Branches
General name Of Enzyme: Debranching enzyme
Two enzymatic activities (Bifunctional enzyme)
1.Transferase Activity
2.Glucosidase Activity

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GLYCOGENOLYSIS (cont):
• Transferase activity:
 Removes chain of 3 glucose residue from
branch
 Transfer them to the non-reducing end of linear
glycogen chain
 α-1,4 bond is broken and another α-1,4 bond is
made.

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GLYCOGENOLYSIS (cont):
• Glucosidase
Activity:
Breaks the α-1,6 bond at branch point
Action is hydrolytically
Releases a free glucose

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GLYCOGENOLYSIS (cont):
• Glycogen Debranching Enzyme:
α-(1—>4) transglycosylase
Glucoseα-(1—>6) glucosidase
Limit Branch (4 residues)
(group transfer reaction)

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GLYCOGENOLYSIS (cont):
The remaining molecule of
glycogen is again available for
the action of phosphorylase
enzyme

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GLYCOGENOLYSIS (cont):
The third and last stage converts G1P (glucose-1-
phosphate) to G6P (glucose-6-phosphate) through
the enzyme phosphoglucomutase.
G1P ↔ G6P
3rd
step: formation of free glucose
and glucose-6-phosphate
Catalysed By Phosphoglucomutase

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GLYCOGENOLYSIS (cont):

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GLYCOGENOLYSIS (cont):
• FATES OF GLUCOSE 6
PHOSPHATE:
IN MUSCLES:
This G6P can enter glycolysis and serve
as an energy source to support muscle
contraction.
IN LIVER:
It releases glucose into blood when blood
glucose level drops.

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GLYCOGENOLYSIS (cont):

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GLYCOGENOLYSIS (cont):
• Tissue which has Glucose 6 phosphatase can generate
free glucose.
• LIVER KIDNEY INTESTINE HAVE THE ENZYME:
The end product of glycogenolysis is free glucose
which entors to the blood stream
• MUSCLES BRAIN AND ADIPOSE TISSUES DON'T
HAVE THE ENZYME:
glycogen breakdown leads to the formation of glucose
6 phosphate which is then metabolized via glycolysis and
TCA cycle

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GLYCOGENOLYSIS (cont):
glycogenolysis
(1).mp4
• WATCH THIS VIDEO ANIMATION

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Thank you