The key enzyme that converts trypsinogen to trypsin is?

NVS- 2025

Biochemistry & Nutrition

Easy

Appeared in: NVS- 2025

Explanation

Enteropeptidase (also called enterokinase) is the specific enzyme responsible for the initial conversion of inactive trypsinogen to active trypsin.
It is located on the brush border of the duodenal mucosa, ensuring activation occurs only within the small intestine.
This activation is the first and most critical step in a cascade that activates all other pancreatic proteolytic enzymes.
Once a small amount of trypsin is formed, it can then activate other zymogens, including more trypsinogen, chymotrypsinogen, and proelastase.

Option A: Elastase is a proteolytic enzyme, but it is secreted as an inactive zymogen (proelastase) and is activated by trypsin. It does not activate trypsinogen.
Option C: Secretin is a hormone, not an enzyme. Its primary role is to stimulate the pancreas to secrete a bicarbonate-rich fluid to neutralize stomach acid in the duodenum.
Option D: Chymotrypsin is another powerful proteolytic enzyme, but like elastase, it is secreted as an inactive zymogen (chymotrypsinogen) and is activated by trypsin. It does not activate trypsinogen.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Enzymatic activation of pancreatic proteases in the digestive system as background academic context rather than a clinical decision trigger.
Understanding this activation pathway is fundamental to comprehending protein digestion and the pathophysiology of malabsorption syndromes.
The principle of secreting inactive zymogens is a key protective mechanism for the pancreas. Failure of this system leads to acute pancreatitis, where activated enzymes autodigest the gland.
A congenital deficiency of enteropeptidase is a rare genetic disorder that causes severe protein malabsorption and failure to thrive in infants because the entire proteolytic cascade cannot be initiated.

How to Approach the Question

First, identify the core of the question: it asks for the specific enzyme that starts the conversion of an inactive form (trypsinogen) to an active form (trypsin).
This is a factual recall question based on digestive physiology.
Analyze the options to differentiate their roles. Recognize that Secretin is a hormone, not an enzyme involved in this specific conversion, which makes it an unlikely answer.
Recall the sequence of protein digestion in the small intestine. Pancreatic enzymes are released as inactive precursors (zymogens) to prevent self-digestion of the pancreas.
Remember that there is a specific 'trigger' or 'starter' enzyme located in the intestine itself. This enzyme is Enteropeptidase.
Differentiate this initial activator from the enzymes that are activated later in the cascade (like Chymotrypsin and Elastase), which are themselves activated by trypsin.

Concept Tested & Keywords

Concept Tested: Enzymatic activation of pancreatic proteases in the digestive system.
Stem keywords: enzyme, converts, trypsinogen, trypsin
Lead-in keywords: is

Q_ntrlVrCz7XSH73eXgI6N

E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) p. 74-76

E6 Physiology Guyton 4SAE Part 2A p. 174-176