Angiotensin II, vasopressin, and glucagon increase or decrease the phosphorylation of phosphorylase, glycogen synthase, and pyruvate kinase in hepatocytes, and these phosphorylation changes are associated with corresponding changes in the enzymatic activity of these proteins.

When angiotensin II or vasopressin binds to liver cells, it releases calcium inside the cell, which turns on enzymes that add phosphate groups to three key proteins: one that breaks down glycogen, one that builds glycogen, and one that uses sugar for energy. This makes the glycogen-breaker more active and the other two less active. When glucagon binds, it triggers a different signal inside the cell using a molecule called cAMP, which also adds phosphate groups to the same three proteins, producing the same changes in their activity. The result is that the liver stops storing sugar and starts releasing it into the blood.