GLYCOGENOLYSIS

     Glycogenolysis is the degradation of stored glycogen producing free glucose and glucose-1-phosphate.

There are three different steps of glycogen degradation.

·          Phosphorylases

·          Removal of branches

·          Formation of free glucose

 

STEP-1:   PHOSPHORYLASES:

PHOSPHORYLASES 

1.              The enzyme “glycogen phosphorylase” is used.

2.              It cleaves α-1,4-linkages from non-reducing ends till four glucose molecules are not left.

3.              It produces glucose-1-phosphate “but” the activity of phosphorylase enzymes stops when it is four residues away from branched point.

4.      Step-1:        Phosphorylases

 

STEP-2:   REMOVAL OF BRANCHES:

REMOVAL OF BRANCHES 

Two enzymatic functions are involved  (bi function enzymes).

·         Transferase activity

·         Glucosidase activity

1.  Transferase Activity:

      .   It removes chain of three glucose residues from the branch.

      .   Transfer them to the non-reducing end of the linear glycogen chain.

 

    .   Transfer them to the non-reducing end of the linear glycogen chain.

    .   α-1,4-linkages is broken down and another α-1,4-linkages is made.

 

2.  Glucosidase Activity:

      .   Breaks the α-1,6-linkages at a branch point.

      .   Action id hydrolytically.

      .   Release a free glucose.

 

Step-2:        Removal of branches

 

STEP-3:     FORMATION OF FREE GLUCOSE:

.    Catalyzed by phosphoglucomutase is used

·            The 3^rd and last stage converts G1P (glucose-1-phosphate)  to G6P (glucose-6-phosphate) through the enzyme phosphoglucomutase.

.    The product on this step is in the form of fat tissue.

 

Step-3:    Formation of free glucose

   

  Formation of free glucose