Which pancreatic zymogen is activated to its active form by the brush-border enzyme enteropeptidase (enterokinase) to help digestion?

• A. Chymotrypsinogen
• B. Trypsinogen
• C. Amylase
• D. Procarboxypeptidase

Answer: (B)

The main concept here is how the pancreatic protease activation cascade starts in the intestine. Enteropeptidase, a brush-border enzyme, cleaves a small peptide from trypsinogen to convert it into active trypsin. Once trypsin is active, it then activates other digestive zymogens—such as chymotrypsinogen and the procarboxypeptidases—by proteolytic cleavage. So the zymogen that enteropeptidase directly activates is trypsinogen, initiating the cascade that enables protein digestion. Amylase is already active when secreted, and the other zymogens require trypsin for activation rather than being directly activated by enteropeptidase.