Download - Glycogenolysis Basic
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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 (14) glycosidic bond = 90% Branched linkage having (16) 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 phosphorylaseAction: Cleavage of α(1→4)linkagesPosition: non-reducing endsProduct: glucose-1-phosphate
BUTActivity 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 Activity2.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:
-(1—>4) transglycosylase
Glucose-(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