Which pancreatic enzyme is secreted in an inactive zymogen form and requires enterokinase (enteropeptidase) for activation in the small intestine?

Explanation

## Pancreatic Enzyme Activation Cascade ### Trypsinogen Activation **Key Point:** Trypsinogen is the inactive precursor of trypsin. It is the ONLY pancreatic enzyme that requires enterokinase (enteropeptidase) for its initial activation in the duodenum. ### Activation Mechanism 1. Trypsinogen is secreted by pancreatic acinar cells in inactive form 2. Enterokinase (produced by duodenal mucosa) cleaves a specific peptide bond 3. Active trypsin is generated 4. Trypsin then auto-activates remaining trypsinogen molecules (cascade amplification) 5. Trypsin also activates other pancreatic zymogens (chymotrypsinogen, proelastase, procarboxypeptidases) ### The Enterokinase Connection **High-Yield:** Enterokinase deficiency is a rare genetic disorder causing severe protein malabsorption because trypsinogen cannot be activated, blocking the entire cascade of pancreatic enzyme activation. ### Other Pancreatic Enzymes | Enzyme | Zymogen Form | Activation | Activator | |--------|--------------|------------|----------| | Trypsin | Trypsinogen | Yes | Enterokinase (then auto-activation) | | Chymotrypsin | Chymotrypsinogen | Yes | Trypsin | | Elastase | Proelastase | Yes | Trypsin | | Amylase | None (secreted active) | No | — | | Lipase | None (secreted active) | No | — | | Phospholipase A2 | Prophospholipase A2 | Yes | Trypsin | **Clinical Pearl:** Acute pancreatitis can occur when trypsinogen is prematurely activated within the pancreas itself, leading to autodigestion and inflammation. **Mnemonic:** **TENT** = **T**rypsinogen needs **E**nterokinase for **N**ew **T**rypsin formation