Question

Chymosin is an example of

• A. Tripeptidase
• B. Dipeptidase
• C. Endopeptidase
• D. Exopeptidase

Hint:

Proteolytic Enzyme Classes:
Chymosin (Rennin), Pepsin, Trypsin, Chymotrypsin = ENDOPEPTIDASES (Cleave internal peptide bonds).
Carboxypeptidases, Aminopeptidases = EXOPEPTIDASES (Cleave terminal residues).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Protease catalytic classification: Chymosin (rennin) is an aspartic endopeptidase (EC 3.4.23.4) that hydrolyzes specific internal peptide bonds within polypeptide chains rather than terminal amino/carboxyl ends.
Key Formula or Approach:
\[ \text{Chymosin (EC 3.4.23.4)} \implies \mathbf{Endopeptidase \text{ (Hydrolyzes internal peptide bond Phe105-Met106)}} \]

Step 2: Detailed Explanation:
Classification of proteolytic enzymes (proteases peptidases):
1. Exopeptidases: Hydrolyze peptide bonds at the terminal ends of protein chains (e.g., Aminopeptidases at N-terminus, Carboxypeptidases at C-terminus).
2. Endopeptidases (C): Hydrolyze internal peptide bonds located inside (within) the polypeptide chain.
- Chymosin (Rennin) is an Aspartic Endopeptidase (EC 3.4.23.4) containing two catalytic aspartate residues (Asp32 and Asp215). It specifically targets and hydrolyzes the internal peptide bond between Phenylalanine-105 and Methionine-106 of the 169-amino-acid $\kappa$-casein molecule, demonstrating strict internal endopeptidase specificity.

Step 3: Final Answer:
Therefore, Chymosin is an example of Endopeptidase, corresponding to option (C).