Zymogen

A zymogen, also known as a proenzyme, is an inactive precursor of an enzyme. Zymogens are synthesized and stored in an inactive state within cells, particularly in the pancreas and stomach. They are typically large proteins that undergo proteolytic cleavage, a process where specific peptide bonds are broken, to become active enzymes. This mechanism prevents the enzyme from prematurely digesting the cells that produce them or the tissues in which they reside. The activation is often triggered by a specific signal, such as a change in pH, the presence of another enzyme, or a particular substrate. Zymogens provide a controlled means of enzyme activation, ensuring that enzymatic activity occurs only when and where it is required.

Zymogen meaning with examples

• The pancreas produces digestive enzymes, like trypsinogen, in the form of zymogens to prevent autodigestion. Upon entering the duodenum, trypsinogen is cleaved into active trypsin by enteropeptidase, initiating a cascade of enzyme activation.
• Pepsinogen, the zymogen of pepsin, is secreted by chief cells in the stomach. The acidic environment of the stomach, particularly in the presence of hydrochloric acid, facilitates the autocatalytic cleavage of pepsinogen into active pepsin.
• Blood clotting involves a complex cascade of zymogen activation. Factors such as prothrombin (zymogen form of thrombin) and fibrinogen are sequentially converted into active enzymes, leading to the formation of a blood clot.
• A researcher is studying the activation of the zymogen pepsinogen by hydrochloric acid to gain insight into the mechanisms that prevent auto-digestion of stomach cells.
• Scientists are trying to create an artificial enzyme that functions by the same activation mechanism, as the zymogen trypsin, that can be used in specific medical application.