Instead, they can release that glucose into the blood to basically increase the concentration of glucose in the blood when the blood glucose levels drop below normal. Now, how exactly is glycogen breakdown controlled in the liver? So in the liver, we also regulate the breakdown of glycogen by regulating the allosteric enzyme we call glycogen phosphorylase. But the glycogen phosphorase inside liver cells is slightly different than the phosphorase that we find inside skeletal muscle cells. So essentially, the liver phosphorase is an isozyme version of the muscle phosphorase. They're pretty much the same molecule with some minor differences.