What is the function of enterokinase in digestion?

• A. Activates trypsinogen into trypsin
• B. Activates chymotrypsinogen into chymotrypsin
• C. Inhibits pepsin activity
• D. Stimulates bile secretion

Answer: (A)

Enteropeptidase on the intestinal brush border initiates the pancreatic protease activation cascade by cleaving trypsinogen to form active trypsin. Once trypsin is active, it activates other pancreatic zymogens such as chymotrypsinogen and procarboxypeptidases, amplifying protein digestion in the small intestine. It does not inhibit pepsin in the stomach, nor does it directly stimulate bile secretion; those processes are controlled by different factors. Chymotrypsinogen is activated indirectly through trypsin, not by enterokinase itself. So the essential function is to generate active trypsin from trypsinogen, starting the downstream activation of digestive proteases.