Zymogens are functionally inactive precursors of enzymes that undergo various transformations (i.e., cleavage by specific endo- or exopeptidases or hydrolysis), resulting in the formation of a catalytically active enzyme. The physiological role of zymogens is that tissues producing enzymes are not exposed to these enzymes. As a result, they are protected from the damage that can be caused by the enzyme inside cells. Therefore, the production of the enzyme is separated from its activation in space. The examples include pepsinogen (pepsin), trypsinogen (trypsin), prorenin (renin), etc.