Enterokinase (Enteropeptidase): Its Role in Protein Digestion

Enterokinase (also known as enteropeptidase) is a crucial digestive enzyme, but it is not a component of pancreatic juice. Instead, it is produced by the brush border cells of the duodenal and jejunal mucosa (the lining of the small intestine).

Function in Protein Digestion

1. Activation of Trypsinogen: The pancreas secretes the inactive proenzyme trypsinogen into the small intestine. Enterokinase cleaves trypsinogen to form active trypsin.
2. Cascade Activation: Once formed, trypsin activates other pancreatic proenzymes: chymotrypsinogen to chymotrypsin, proelastase to elastase, and procarboxypeptidases to carboxypeptidases.
3. Protein Breakdown: These active proteases then break down dietary proteins into smaller peptides and amino acids for absorption.

Without enterokinase, the entire pancreatic proteolytic cascade would not initiate efficiently, leading to severe protein malabsorption. Congenital enterokinase deficiency is a rare but serious condition causing protein-losing enteropathy in infants.