What is the function of trypsin in protein digestion?

Question

BlackTom AI · Accepted Answer

Trypsin is a pancreatic serine protease that both digests proteins and activates other proteolytic zymogens.

1) Relevant knowledge points and concepts
- Trypsin is produced in the pancreas as the inactive zymogen trypsinogen.  
- Enterokinase (enteropeptidase) on the duodenal brush border cleaves trypsinogen to active trypsin.  
- Trypsin is an endopeptidase with specificity for cleaving peptide bonds on the carboxyl side of basic amino acids (lysine and arginine).  
- Trypsin participates in a proteolytic activation cascade: once active, it converts other pancreatic proenzymes (e.g., chymotrypsinogen, proelastase, procarboxypeptidases) into their active forms.

2) Step-by-step reasoning
- Step 1: Trypsinogen is secreted into the small intestine.  
- Step 2: Enterokinase cleaves a specific activation peptide from trypsinogen → active trypsin.  
- Step 3: Active trypsin cleaves peptide bonds in dietary proteins, reducing them to smaller peptides and amino acids suitable for absorption.  
- Step 4: Active trypsin also cleaves and activates other pancreatic zymogens, amplifying proteolytic activity in the intestinal lumen.

3) Calculations
- No numerical calculations are required for this conceptual question.

4) Why the correct answer is correct
Option (a) states that trypsin "activates other proteases and digests proteins," which directly summarizes the dual role described above: proteolytic digestion of proteins and protease activation in the pancreatic enzyme cascade.

5) Why the other options are incorrect
- (b) "Cleaves peptide bonds at aromatic amino acids" describes chymotrypsin (prefers aromatic residues like phenylalanine, tyrosine, tryptophan), not trypsin.  
- (c) "Digests lipids" refers to lipases, not trypsin.  
- (d) "Breaks down carbohydrates" refers to amylases and other carbohydrases, not trypsin.

6) Conclusion
Because trypsin both hydrolyzes peptide bonds in proteins (preferring basic residues) and activates other pancreatic proteases by proteolytic cleavage, the correct answer is a. Activates other proteases and digests proteins, which matches the provided answer.

What is the function of trypsin in protein digestion?单项选择题

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