Biochemistry/Glycogenolysis

Question

a) Outline how glycogenolysis is regulated in the liver and muscle. [10] 

Answer 1

There are two enzymes which regulate glycogenolysis, or glycogen breakdown, in the muscles and liver. They are phosphorylase kinase and glycogen phosphorylase. Both are activated by phosphorylation.

In muscle, cAMP binds phosphorylase kinase which is then activated and can convert phosphorylase b to phosphorylase a. Phosphorylase a is able to catalyze the breakdown glycogen.

In the cytosol, glycogen phosphorylase catalyzes the release of glucose-1-phosphate from glycogen with the use of inorganic phosphate to cleave alpha-1,4 bonds. Glucose-1-phosphate can then convert to glucose-6-phosphate.