During protein digestion, the activation of pancreatic zymogens in the small intestine relies on a cascade initiated by trypsin. Once trypsinogen is activated into trypsin by enteropeptidase on the intestinal brush border, trypsin cleaves and activates other inactive zymogens. It converts chymotrypsinogen into chymotrypsin, proelastase into elastase, and procarboxypeptidase into carboxypeptidase. Trypsin can also activate additional trypsinogen molecules through autoactivation. This cascade ensures that these powerful proteases remain inactive while stored in the pancreas, preventing tissue damage, and only become active upon reaching the intestinal lumen.