And if we want to go in reverse, if we want to remove that P and add that P onto that ADP to reform the ATP and that active enzyme or in some cases inactive enzyme, we use protein phosphatase and we'll discuss these proteins in detail in future electrodes. Now, the third mechanism of control is proteolytic activation or proteolytic cleavage. Now, many enzymes produced by the cells of our body are produced in their inactive form. So the precursor inactive form of an enzyme is called a zymogen or sometimes a proenzyme. Now, in order to activate these zymogens, these pro enzymes, special molecules called proteases, which we spoke about previously, are basically used to cleave s special sites and that is what activates these polypeptides, these zymogens. And once activated, they can basically carry out their functionality until they are inhibited by some type of inhibitor, usually an irreversible inhibitor.