Glycogen Hydrolysis

Glycogen hydrolysis


In this experiment, the hydrolysis of the storage (liver) polysaccharide glycogen a branched polymer of glucopyranose residues, will be followed with time, either in the presence of H+ (as 2M HCL), or the enzyme α-amylase from the bacterium Bacillus subtilis.


Glycogen is a major storage polysaccharide and is the storage polysaccharide in animals, mainly in liver, and in muscles. It’s more highly branched and is hydrolyzed by the enzyme α-amylase, which is found in saliva and pancreatic juice. Its function is as an energy (glucose) reserve, polymer made up of glucose subunits highly branched molecules with a1-6 branch points a 1-4 linked glucopyranose residues: “Starches” structure permits rapid release of glucose from glycogen stores into the blood. The highly branched nature of glycogen allows hydrolytic enzymes to have many chain ends from which glucose molecules can be hydrolyzed.

Acid hydrolysis is the most common method for hydrolyzing a glycogen sample before glucose analysis. The acid hydrolysis technique can contribute to the variation of analysis; the composition of glycogen can be demonstrated in vitro by totally hydrolysing it in the presence of acid. The acid hydrolysis of glycogen does not take place immediately; rather it takes place over a period of time. One can then follow the process of the reaction from beginning to end by removing small samples at predetermined time intervals and assaying them for glucose. Initially, little or no glucose is evident, but as the reaction progresses,

increasingly more glucose are released until all of the glycogen is degraded. In the cell (in vitro) glycogen functions as a storehouse of glucose, this can be utilised by the cell for the generation of energy in the form of ATP.

The cell possesses a variety of enzymes (hydrolases such as a-amylases and a glycosidases) which achieve the hydrolysis of glycogen at or near neutrality. The hydrolysis by glycogen by...