This slide share deals with Glycogenesis ,Glycogenolysis and the regulation of Glycogenesis and Glycogenolysis . -by Dharshini.K , I pharm .D

1. GLYCOGEN
METABOLISM
BY
K.DHARSHINI
I PHARM d
RVS
RVS COLLEGE OF PHARMACEUTICAL SCIENCES
SULUR, COIMBATORE, TAMIL NADU, INDIA.

2. GLYCOGEN
Glycogen is
generally a
polymer of glucose
This slide share deals with :
1. Glycogenesis
2. Glycogenolysis
3. Regulation of
glycogenesis and
Glycogenolysis

3. STRUCTURE
OF GLYCOGEN
Representation of the bonds
present in glycogen (*follow the
colors)

4. GLUCOSYL
RESIDUE(glucose
monomer)
NON-REDUCING
END
2. GLYCOGENIN
(protein core)

5. GLYCOGENESIS

6. • Step1:Synthesisofuridinediphosphateglucose
• Step2:Synthesisofaprimertoinitiateglycogen
synthesis
• Step3:Elongationofglycogenchains
• Step4:Formationofbranches
• Step5:Repetitionofstep3and4isdonetoforma
glycogenpolymer
MAJOR STEPS INVOLVED IN GLYCOGENESIS:

7. STEP 1:
• The enzymes hexokinase and glucokinase convert glucose to glucose 6
phosphate
• Phosphoglucomutase catalyses the Conversion of glucose 6 phosphate to
glucose 1 phosphate
• Uridine di phosphate glucose ( UDGP) is synthesized from glucose1 phosphate
and utp by udp glucose pyrophosphorylase
STEP 2 :
• A small fragment of pre-existing glycogen must act as a primer to initiate
glycogen synthesis
• the enzyme glycogen initiator synthase transfers the first molecule of glucose to
glycogenin
• Then glycogenin itself takes up a few glucose residues to form a Fragment of
primer

8. STEP 3 :
• Glycogen synthase is responsible for the formation of 1,4 glycosidic linkages
• This enzyme transfers the glucose from UDPG to the non –reducing end of glycogen to form alpha 1,4
linkages
STEP 4 :
• The formation of branches is brought by the action of a branching enzyme,
• Namely glucosyl alpha 4,6 transferase
• This enzyme transfers a small fragment of 5 to 8 glucose residues from the non reducing end of
glycogen chain to another glucose residue where it is linked with alpha 1,6 bond
• This leads to the formation of a new non reducing end besides the existing one
• Glycogen is further elongated and branched by the enzymes glycogen synthase and glucosyl 4-6
transferase

9. P
A
T
H
W
A
Y

10. The overall reaction of the glycogen synthesis for the
addition of each glucose residue
(GLUCOSE) n +GLUCOSE +2ATP
 (GLUCOSE) n+1 +2ADP +Pi

11. GLYCOGENOLYSIS

12. MAJOR STEPS INVOLVED IN GLYCOGENOLYSIS :
• Step1:Shorteningofchains
• Step2:Removalofbranches
• Step3:Conversionofglucose1phosphatetoglucose6
phosphateviaenzymephosphoglucomutase

13. Step 1 :
• The alpha 1,4 glycosidic bonds Are cleaved sequentially by the enzyme glycogen phosphorylase
to yield glucose 1-phosphate (phosphorolysis)
• The glycogen so formed is known as limit dextrin
• Glycogen phosphorylase possesses a molecule of pyridoxal phosphate
Step 2 :
• The branches of glycogen are cleaved by two enzyme activities present on a single polypeptide
called debranching enzyme
• Glucosyl 4:4 transferase removes a fragment of 3 or 4 glucose residues attached at a branch and
transfers them to another chain
• Here one alpha 1,4 cleaved and the same alpha 1,4 bond is made but the places are different
• Amylo alpha 1,6 glucosidase breaks the alpha 1,6 bond
• The remaining molecule of glycogenis again available for the action of phosphorylase and
debranching enzyme to repeat the reactions

14. Step 3 :
• Through the combined action of glycogen phosphorylase and debranching
enzyme glucose 1 phosphate and free glucose In a ratio of 8:1 are produced
• Glucose 1 phosphate is converted to glucose 6 phosphate by the enzyme
phosphoglucomutase
• The fate of glucose 6 phosphate depends on the tissue
• The liver, kidney ,and intestine contain the enzyme glucose 6 phosphatase
that cleaves glucose 6 phosphate to glucose

15. P
A
T
H
W
A
Y

16. The liver is the major
glycogen storage organ to
provide glucose into the
circulation to be utilized by
various tissue

17. REGULATION OF
GLYCOGENESIS
AND
GLYCOGENOLYSIS

18. Dephosphorylation
(Snthase Phosphatase)
Synthase d
Synthase
I
• Glycogen synthase is present in muscle and liver in two interconvertible form
• Synthase d is the dependent form and inactive form of the enzyme
• Synthase I is the independent form And active form of the enenzyme
• Synthase I is converted into synthase d by phosphorylation
• Synthase d is converted to synthase I by the enzyme synthase phosphatase by
dephosphorylation
Phosphorylation
GLYCOGEN SYNTHASE
OR GLUCOSYL TRANSFERSAE

19. PHOSPHORYLASE
Active
Phosphorylase
A
Inactive
Phosphorylase
B
• Phosphorylase exist in two forms
• The active phosphorylase a splits glucose 1 phosphate units from
glycogen
• The inactivated form is activated in presence of atp by a specific
phosphorylase kinase which is in turn stimulated by cyclic AMP

20. A good coordination and regulation of glycogen synthesis and it’s
degradation are essential to maintain the blood glucose levels. Glycogenesis
and Glycogenolysis are respectively controlled by glycogen synthase and
glycogen phosphorylase. regulation of these enzymes is accomplished by
three mechanisms
• ALLOSTERIC REGULATION
• HORMONAL REGULATION
• INFLUENCE OF CALCIUM

21. RECOLLECTION
WALL

23. ACKNOWLEDGEMENT
SINCERE THANKS TO
1. MR. S. S. Rajendran M. Pharm for his constant
support and supervision
2. The Library faculties of RVS COPS, Coimbatore, India
for their help with the requirements
3. Heart felt thanks to all professors and parents for
their cooperation regarding this slide share

24. The End