Which brush border enzyme converts trypsinogen from the pancreas into active trypsin?

1. The pancreas makes its protein-digesting enzymes in inactive forms so they cannot digest the pancreas itself. 2. Activation therefore has to happen after the juice has reached the duodenum. 3. Enteropeptidase, an enzyme of the intestinal brush border, converts trypsinogen into trypsin. 4. Trypsin then converts procarboxypeptidase and chymotrypsinogen into carboxypeptidase and chymotrypsin. 5. So chymotrypsin and carboxypeptidase are products of that cascade, not its trigger. 6. Aminopeptidase is a brush border enzyme too, but it acts on the amino end of peptides. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 23 "The Digestive System", section 23.6 Accessory Organs in Digestion: The Liver, Pancreas, and Gallbladder_