The biochemical change usually occurs in Golgi bodies, where a specific part of the precursor enzyme is cleaved in order to activate it.
[citation needed] The pancreas secretes zymogens partly to prevent the enzymes from digesting proteins in the cells in which they are synthesised.
Accidental activation of zymogens can happen when the secretion duct in the pancreas is blocked by a gallstone, resulting in acute pancreatitis.
The external environment has a different pH than inside the fungal cell and this changes the zymogen's structure into an active enzyme.
In the duodenum, the pancreatic zymogens, trypsinogen, chymotrypsinogen, proelastase and procarboxypeptidase, are converted into active enzymes by enteropeptidase and trypsin.