Pancreatic proteases are secreted as inactive zymogens. Which enzyme, anchored on the duodenal brush border, initiates the cascade that activates them?

• A Pepsin regurgitated from the stomach, which cleaves chymotrypsinogen
• B Enteropeptidase (enterokinase), which converts trypsinogen to trypsin ✓
• C Carboxypeptidase A, which autocatalyses procarboxypeptidase B
• D Pancreatic lipase, which exposes active sites on proelastase

Explanation

Enteropeptidase is a brush border enzyme of the duodenum that cleaves a hexapeptide from trypsinogen, generating active trypsin. Trypsin then activates the remaining zymogens, chymotrypsinogen, procarboxypeptidases, proelastase and prophospholipase B2, as well as more trypsinogen. Premature intrapancreatic activation of trypsinogen is the central event proposed for acute pancreatitis. Pepsin plays no role in intestinal proteolytic activation.

Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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