Pancreatic proteases (e.g., trypsin) are secreted as inactive zymogens. Why is zymogen secretion important, and what activates them in the small intestine?

• A. Zymogen secretion prevents autodigestion of the pancreas; enterokinase (enteropeptidase) on the duodenal brush border activates trypsinogen to trypsin, which then activates other proteases.
• B. Secreting active proteases would improve digestion efficiency, so zymogen secretion is an evolutionary error corrected by intrapancreatic inhibitors rather than activation in the intestine.
• C. Zymogens are secreted to speed up hormone release from the pancreas, with insulin serving as the primary molecular activator for all zymogens once food reaches the ileum.
• D. Zymogen secretion increases protease activity inside the pancreas to help digest endogenous proteins during fasting; pepsin from the stomach is the activator of pancreatic zymogens in the duodenum.

Answer: (A)