Enterokinase activates which enzyme in digestion?

• A. Trypsinogen
• B. Chymotrypsinogen
• C. Pepsinogen
• D. Lipase

Answer: (A)

Enterokinase, a duodenal brush-border enzyme, activates the pancreatic zymogen trypsinogen to active trypsin by cleaving after a specific lysine residue in the DDDDK motif. Once trypsin is active, it not only digests proteins directly but also activates other pancreatic proenzymes, amplifying the proteolytic cascade essential for digestion. The other enzymes aren’t activated directly by enterokinase—chymotrypsinogen needs trypsin for activation, pepsinogen is activated in the stomach by acid and pepsin, and lipase is not activated by enterokinase.