Question

1- Answer the following questions regarding glycogen phosphorylase.

a. The V_maxof the glycogen phosphorylase from skeletal muscle is much greater than the V_maxof the same enzyme from liver tissue. Explain the physiological rationale of this kinetic difference considering the function of the enzyme in muscle compared to liver

2. A biochemical test shows that an individual lacks the muscle form of glycogen phosphorylase.
   1. What would be the biochemical consequence of this metabolic defect? (i.e. what pathway is affected and in what way?)
   2. What would be the physiological consequence for the person?

Answer 1

1.

a) The V_maxof the glycogen phosphorylase from skeletal muscle is much greater than the V_maxof the same enzyme from liver tissue because in actively working the muscle, ATP flux requirements are very high and glucose 1-phosphate must be produced rapidly to eventually go into the glycolysis cycle as glucose 6 phosphate, therefore the muscle enzyme requires a high Vmax.