| Proteolytic activation of digestive enzymes
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| Some enzymes are stored in a specific organelle or compartment, such as exocytotic vesicles in cells, in inactive precursor forms termed proenzymes or zymogens. This type of enzyme includes the digestive enzymes, which are stored as inactive zymogens in the pancreas. The zymogens are secreted in pancreatic juice following a meal and are activated in the gastrointestinal tract; trypsinogen is converted into trypsin by the action of intestinal enteropeptidase. Enteropeptidase, located on the inner surface of the duodenum, hydrolyzes an N-terminal peptide from the inactive trypsinogen. Rearrangement of the tertiary structure yields the proteolytically active form of trypsin. The active trypsin then proteolytically digests other zymogens, such as procarboxypeptidase, proelastase and chymotrypsinogen, as well as other trypsinogen molecules. Similar proteolytic cascades are observed during blood clotting and fibrinolysis (dissolution of clots) (Chapter 6).
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Since the pancreas is an important organ for controlling blood glucose , the unregulated activation of these enzymes would cause inflammation of the pancreas (pancreatitis).
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