Question

Given below are two statements:
Statement (I): Chymosin is an example for endopeptidase
Statement (II): Bovine Chymosin has Asp-Thr-Gly amino acid residues in its active site
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are correct
• B. Both Statement (I) and Statement (II) are incorrect
• C. Statement (I) is correct but Statement (II) is incorrect
• D. Statement (I) is incorrect but Statement (II) is correct

Hint:

To remember enzyme classifications and active sites:
- Chymosin \(\rightarrow\) Endopeptidase (cleaves internal bonds specifically).
- Aspartic protease family \(\rightarrow\) Active site contains two conserved Asp-Thr-Gly (D-T-G) motifs.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Chymosin (also known as rennin) is the primary proteolytic enzyme found in rennet, extracted from the abomasum of young calves.
It is a highly specific aspartic protease widely used in cheesemaking to cleave milk proteins.

Step 2: Detailed Explanation:
Let us evaluate both statements:
-Statement (I): "Chymosin is an example for endopeptidase."
This statement is correct.
Proteases are classified into exopeptidases (which cleave terminal amino acids from the ends of polypeptide chains) and endopeptidases (which hydrolyze internal peptide bonds within the polypeptide chain).
Chymosin specifically cleaves the internal \(\text{Phe}_{105}-\text{Met}_{106}\) peptide bond of \(\kappa\)-casein, making it a classic example of an endopeptidase.
-Statement (II): "Bovine Chymosin has Asp-Thr-Gly amino acid residues in its active site."
This statement is correct.
Chymosin belongs to the family of aspartic proteases (acid proteases).
The catalytic mechanism of these enzymes relies on two conserved aspartic acid residues located in the active site cleft.
These active site residues reside within the highly conserved signature motif:
\[ \text{Asp}-\text{Thr}-\text{Gly} \quad (\text{D-T-G}) \]
These residues coordinate a water molecule that participates in the nucleophilic attack on the target peptide bond, enabling efficient cleavage under acidic conditions.
Therefore, both Statement (I) and Statement (II) are correct.

Step 3: Final Answer:
Both Statement (I) and Statement (II) are correct, which corresponds to Option (A).