Now to actually activate these enzymes we have to basically cleave the enzymes as specific peptide bonds. So sometimes we cleave one peptide bond, sometimes we cleave many peptide bonds, but the end result is the same exact when our enzymeogen undergoes proteolytic activation, proteolytic cleavage, by some type of protease we basically produce the fully functional form of that enzyme. Now when we discussed the process of phosphorylation we said that only those enzymes and proteins that are found inside our cells can actually be controlled via the process of phosphorylation. And that's because phosphorylation actually requires the presence of ATP. And ATP molecules are found abundantly only inside our cells. So that means phosphorylation can control only those enzymes and proteins which exist inside our cells.