Glycogen is the storage form of glucose found mainly in the liver and muscle. Glycogen metabolism involves glycogenesis, the formation of glycogen from glucose, and glycogenolysis, the breakdown of glycogen into glucose. Glycogenesis occurs through three phases - activation of glucose, glycosyl transfer, and branching. Glycogenolysis produces glucose through the actions of phosphorylase and debranching enzymes. Defects in enzymes involved in glycogen synthesis or breakdown can cause glycogen storage diseases, including Von Gierke's disease caused by glucose-6-phosphatase deficiency.

1. 1
GLYCOGEN
METABOLISM
It’s doesn’t matter
what others are doing,
Its matter what you are doing
Believe in yourself
by
Dr. Santhosh Kumar N
Associate Professor of Biochemistry

2.  Storage form of glucose in animals & humans
 Found mainly in cytoplasm of liver and muscle
 It consists of long polymer chains of α-D-
glucose units connected by an α-1,4-glucosidic
bond and α-1,6-glucosidic bonds
GLYCOGEN

3. • Glycogen metabolism mainly consists of two pathways
Anabolic part is Glycogenesis
Catabolic part is Glycogenolysis

4. Glycogenesis
Formation of glycogen from glucose in cytosol of liver
& skeletal muscle

5. • Liver glycogen helps to maintain blood glucose level.
• Muscle glycogen is to act as reserve fuel for muscle contraction
• All the enzymes related to glycogenesis are cytoplasmic
• Dived into 3 phases:
a) Activation of D-Glucose
b) Glycosyl transfer
c) Branching

6. Glucose (6C)
Glucose -6-Phosphate (6C)
Glucose -1-Phospate
ATP
ADP
Hexokinase /
Glucokinase
Phosphoglucomutase
UTP
PPi
Glu-1-P-Uridyl
transferase 2Pi
UDP-Glucose
pyrophosphorylase
UDP-Glucose

7. Glucose (6C)
Glucose -6-Phosphate (6C)
Glucose -1-Phospate
UDP-Glucose
ATP
ADP
Hexokinase /
Glucokinase
Phosphoglucomutase
UTP
PPi
Glu-1-P-Uridyl
transferase
1,4-Glycosyl Units
Glycogen synthase Glycogen Primer
Glycogenin
UDP
2Pi
UDP-Glucose
pyrophosphorylase

8. Glycogenin (Glycogen primer)
• Protein-carbohydrate complex
• Act as dimeric protein having two identical monomers.
• Each monomer added an oligosaccharide chain of 7-
glucose units.
• Glycogen primer is essential to accept the glycosyl units.

9. Glucose (6C)
Glucose -6-Phosphate (6C)
Glucose -1-Phospate
UDP-Glucose
ATP
ADP
Hexokinase /
Glucokinase
Phosphoglucomutase
UTP
PPi
Glu-1-P-Uridyl
transferase
1,4-Glycosyl Units
Glycogen synthase Glycogen Primer
Glycogenin
UDP
9
NEW 1,4 Glycosyl Units

10. Glucose (6C)
Glucose -6-Phosphate (6C)
Glucose -1-Phospate
UDP-Glucose
Glycogen
ATP
ADP
Hexokinase /
Glucokinase
Phosphoglucomutase
UTP
PPi
Glu-1-P-Uridyl
transferase
1,4-Glycosyl Units
Glycogen synthase
Branching Enzyme
Glycogen Primer
Glycogenin
UDP
2Pi
UDP-Glucose
pyrophosphorylase

11. Glycogen
Glucose
Regulation of Glycogenesis

13. Glycogenolysis
(Glycogen Degradation)
Formation of glucose from storage glycogen

14.  Glycogenolysis is not the reverse of glycogenesis
 Glycogen contributes glucose
To glycolysis
To maintain blood glucose (Liver)

15. Phosphorylase Phosphorylase
Highly branched
core
PLP
Glucose-1-P Glucose-1-P

16. Transferase
D-Glucose-1-P
Limit Branch
+
Debranching
enzyme
Phosphorylase

17. Debranching Enzyme
Phosphoglucomutase
Limit Dextrin
Glucose-1-Phosphate
Glucose-6-Phosphate
Glucose
Glucose-6-Phasphatase
Pi
H2O
Pi
Glycogen
Glycogen Phosphorylase
Glucose

18. Regulation of Glycogenolysis
• It regulated by phosphorylase enzyme
• it is stimulated by glucagon & adrenaline, leads to increased synthesis of glucose
from glycogen.
• Phosphorylase inhibited by high conc. of glucose, insulin, leads to inactivates
glycogenolysis.

19. Glycogen Glucose
Regulation

20. produce ATP
for muscle contraction
Glycolysis
Epinephrine
Glucagon &
epinephrine

21. Glycogen Storage
Diseases
Group of genetic diseases, that result from a defect
in enzyme required for either glycogen synthesis or
degradation

22. A 03 months old home delivered male baby was brought to the pediatric OPD.
O/E – doll like face with fat cheeks, thin extremities, protruded abdomen.
Systemic examination: Hepatomegaly +
• Histopathological examination of liver biopsy: Distended hepatocytes with
glycogen & lipid vacuoles.
Blood examination:
Urine analysis: For glucose : Negative
FBS ALT AST ALP Uric
acid
TG Chol Lactate
45mg/dl 150U/L 130U/L 40U/L 9.5mg/dl 300mg/dl 350mg/dl 95mg/dl

23. Von –Gierke’s Diseases
TYPE-I :GLYCOGEN STORAGE DISEASE
Enzyme Defect
Glucose-6-phosphatase
Affected Organ
Liver, Kidney & Intestine
Clinical Features
Hepatomegaly lead to cirrhosis
Growth retardation
Fasting hypoglycemia
Lactic acidosis
Hyperuricemia
Hyperlipidemia
Treatment: To give small quantity of food at frequent
intervals

24. Fasting hypoglycemia
Hyperuricemia
Lactic acidosis
PRPP Purine
Uric acid

25. Type: Name Enzyme Defect Affected Organ Manifestations
Type-I
Von -
Gierke‘s
Disease
Glucose-6-
phosphatase
Liver, Kidney and
Intestine.
Hepatomegaly, progressive
renal disease, growth
retardation
Type-II Pompe’s
Disease
Lysosomal Acid
maltase
Skeletal & Cardiac
muscle
Myopathy, Muscular
dystrophy
Type-III Cori ‘s
Disease
Debranching
enzyme
Liver, skeletal &
cardiac muscle
Infant hepatomegaly,
myopathy
It is a genetic disorder in which abnormal quantities of glycogen are deposited in
the liver, kidney, heart and muscle.

26. Type: Name Enzyme Defect Affected
Organ
Manifestations
Type-IV Amylopectinosis
(Anderson’s
disease)
Branching
enzyme
Liver, muscle Hepatosplenomegaly,
cirrhosis
Type-V Mc Ardle’s
Disease
Muscle
phosphorylase
Skeletal
muscle
Induced cramps & pain,
Myoglobinuria
Type-VI Hers’ disease Liver
phosphorylase
Liver Hepatomegaly,
mild hypoglycemia,
Hyperlipidemia and ketosis,
Type -VII Tarui’s disease Muscle PFK-1 Muscle,
RBC's
Cramps and pain,
Myoglobinuria, & hemolytic
anemia

27. THANK YOU