Now, glycogen for sporlase is actually a dimer molecule. It consists of two polypeptide subunits and it is an allosteric enzyme. What that means is there exists certain types of molecules inside our cells that can actually either inhibit or activate activity of glycogen phosphorase. Now, within skeleton muscle cells, phosphorase exist in two interconvertible forms. We have phosphorase A and we have phosphorase B. Now, each one of these phosphoralase enzymes in turn exist in two different states.