How are pancreatic enzymes activated in the small intestine?

• A. Enzymes produced in active form secreted into small intestine.
• B. Activation by bile acids alone.
• C. Zymogens secreted as inactive proenzymes; enterokinase activates trypsinogen to trypsin; trypsin then activates other enzymes.
• D. Activation occurs in the stomach.

Answer: (C)

Pancreatic enzymes are released as inactive proenzymes to prevent damage to the pancreas. In the small intestine, the brush-border enzyme enterokinase (enteropeptidase) converts trypsinogen into active trypsin. Once trypsin is activated, it acts as the master switch that activates the other pancreatic zymogens—chymotrypsinogen becomes chymotrypsin, proelastase becomes elastase, and procarboxypeptidases become active carboxypeptidases. This sequential activation, driven by trypsin, ensures digestion proceeds only after the chyme reaches the duodenum and appropriate intestinal conditions are present. Bile acids assist digestion but do not activate these proenzymes, and activation of pancreatic enzymes does not occur in the stomach, where pepsinogen is activated to pepsin instead.