This document summarizes glycogen metabolism. Glycogen is a storage form of glucose that is mainly stored in the liver and muscle. It is broken down through glycogenolysis by enzymes like glycogen phosphorylase, glycogen debranching enzyme, and phosphoglucomutase to release glucose-1-phosphate which is converted to glucose-6-phosphate. Glycogenolysis leads to glucose formation in the liver and lactate formation in muscle. Cyclic AMP and insulin regulate glycogenolysis and glycogenesis respectively. Deficiencies in enzymes of glycogen metabolism cause glycogen storage diseases.

1. NAME:RUDRADEEP HAZRA
STREAM-BACHELOR OF PHARMACY
(2ND SEM)
ROLL NO -19301918060.
Glycogen Metabolism
Pathways.

2. Glycogen-Introduction
 Glycogen is a readily mobilized storage form of glucose.
 It is a very large, branched polymer of glucose residues
that can be broken down to yield glucose molecules when
energy is needed.
 Most of the glucose residues in glycogen are linked by α-
1,4-glycosidic bonds.
 Branches at about every tenth residue are created by α-
1,6-glycosidic bonds.

3. Glycogen storage sites
 It is stored mainly in liver and muscle.
 The liver content of glycogen is greater than that of
muscle.
 Since, the muscle mass of the body is considerably
greater than that of the liver, about three-quarters of
total body glycogen is in muscle.

4. Glycogenolysis
 The degradation of stored glycogen to produce
glucose is called glycogenolysis.
 The pathways for the synthesis and degradation of
glycogen are not reversible.
 An independent set of enzymes present in the cytosol
carry out glycogenolysis. Glycogen is degraded by
breaking alpha -1,4 – and alpha -1,6- glycosidic
bonds.

5. Steps of Glycogenolysis
 The glucose units of the outer branches of glycogen
enter the glycolytic pathway through the action of
three enzymes: glycogen phosphorylase,glycogen
debranching enzyme, and phosphoglucomutase.
 Glycogen phosphorylase catalyzes the reaction in
which an (α 1-4) glycosidic linkage between two
glucose residues at a nonreducing end of glycogen
undergoes attack by inorganic phosphate (Pi),
removing the terminal glucose residue as -D-glucose
1-phosphate.

6. Action of debranching enzymes
Transferase and Debranching enzyme-
 The Transferase shifts a block of three glucosyl
residues from one outer branch to the other.
 This transfer exposes a single glucose residue joined
by an α -1,6-glycosidic linkage.
 α-1,6-Glucosidase, also known as the debranching
enzyme, hydrolyzes the α -1, 6glycosidic bond,
resulting in the release of a free glucose molecule.

7. Glucose -6- Phosphate to Glucose
Phosphoglucomutase-
 Glucose 1-phosphate formed in the phosphoroylytic
cleavage of glycogen must be converted into glucose
6-phosphate to enter the metabolic mainstream. This
shift of a phosphoryl group is catalyzed by
Phosphoglucomutase.

8. Glycogen Degradation to Glucose

9. Glycogen Metabolism
 Glycogen represents the principal storage form of
carbohydrate in the body, mainly in the liver and muscle.
 It is broken down by a separate pathway- glycogenolysis.
 Glycogenolysis leads to glucose formation in liver and lactate
formation in muscle owing to the respective presence or
absence of glucose 6-phosphatase.
 Cyclic AMP integrates the regulation of glycogenolysis and
glycogenesis by promoting the simultaneous activation of
phosphorylase and inhibition of glycogen synthase.
 Insulin acts reciprocally by inhibiting glycogenolysis and
stimulating glycogenesis.
 Inherited deficiencies in specific enzymes of glycogen
metabolism in both liver and muscle are the causes of
glycogen storage diseases.

10. Conclusion
 I am very much thankful to my professor to give me
such a wonderful topic to work on.
 Reference –Internet,biochemistry book by
satyanarayana and principles of biochemistry by
A.Leningher.