Zn is present as prosthetic group in this enzyme:
**Core Concept**
Carboxypeptidase A is a zinc-dependent metalloprotease that plays a crucial role in protein digestion. The enzyme's active site contains a zinc ion, which is essential for its catalytic activity.
**Why the Correct Answer is Right**
The zinc ion in carboxypeptidase A serves as a cofactor, facilitating the hydrolysis of peptide bonds. The zinc ion coordinates with the carboxylate group of the substrate, allowing the enzyme to cleave the peptide bond. This process involves the nucleophilic attack of a water molecule on the carbonyl carbon, resulting in the formation of a new carboxylic acid and a free amino acid. The zinc ion is essential for stabilizing the transition state of the reaction and lowering the energy barrier for peptide bond hydrolysis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the enzyme described does not contain a zinc ion as a prosthetic group.
**Option B:** This option is incorrect because the enzyme described does not have a zinc-dependent mechanism of action.
**Option C:** This option is incorrect because the enzyme described does not involve zinc in its catalytic activity.
**Clinical Pearl / High-Yield Fact**
Carboxypeptidase A is an example of a zinc-dependent enzyme, and its activity is crucial for protein digestion in the small intestine. Deficiencies in this enzyme can lead to impaired protein digestion and malabsorption of essential amino acids.
**Correct Answer: C. Carboxypeptidase A.**