Question:
Which of the following is a serine protease?
Which of the following is a serine protease?
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Look for the enzyme with a Ser-His-Asp catalytic triad, not the acid or zinc protease.
Updated On: Jun 24, 2026
- Pepsin
- Trypsin
- Carboxypeptidase
- None
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The Correct Option is B
Solution and Explanation
Step 1: Serine proteases are enzymes that use a catalytic serine residue (part of the Ser-His-Asp catalytic triad) to cleave peptide bonds. The question asks which listed enzyme belongs to this family.
Step 2: Trypsin is the classic example of a serine protease. It is secreted by the pancreas as trypsinogen, activated to trypsin, and cleaves peptide bonds on the carboxyl side of lysine and arginine using its active-site serine.
Step 3: Why the others are wrong: pepsin is an aspartic (acid) protease that works at low gastric pH; carboxypeptidase is a zinc-dependent metalloprotease (metalloexopeptidase). Neither uses a catalytic serine.
Step 4: Therefore the serine protease among the options is trypsin.
Step 2: Trypsin is the classic example of a serine protease. It is secreted by the pancreas as trypsinogen, activated to trypsin, and cleaves peptide bonds on the carboxyl side of lysine and arginine using its active-site serine.
Step 3: Why the others are wrong: pepsin is an aspartic (acid) protease that works at low gastric pH; carboxypeptidase is a zinc-dependent metalloprotease (metalloexopeptidase). Neither uses a catalytic serine.
Step 4: Therefore the serine protease among the options is trypsin.
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