A zymogen is an inactive enzyme precursor, a proenzyme, that displays no catalytic activity until it is transformed into its active form by a process such as the cleavage of one or more peptide bonds. Pancreatic digestive enzymes are secreted as zymogens partly to prevent the enzymes from digesting proteins in the cells in which they are synthesized. An additional important role of zymogen activations occurs in blood clotting. For blood clotting, the response time must be fast in order to achieve clotting at the right spot and time to prevent excessive bleeding. Zymogen cascades are therefore employed to achieve that rapid response in which activation of one clotting factor is then responsible for activating another clotting factor.
Conceptual Vocabulary for Zymogens