Zinc is the key metal cofactor for Carbonic anhydrase, Alcohol dehydrogenase, and Carboxypeptidase. Remembering this group of metalloenzymes is highly helpful for biochemistry questions.
Step 1: Understanding the Concept:
Many enzymes require non-protein chemical components called cofactors to function. These can be organic molecules (coenzymes) or inorganic metal ions (enzyme activators). Zinc (\(Zn^{2+}\)) is a crucial divalent metal ion activator for several key enzymes. Step 2: Detailed Explanation:
Let us examine the enzyme relationships:
Carbonic anhydrase is a metalloenzyme that catalyzes the rapid interconversion of carbon dioxide and water into carbonic acid, bicarbonate, and protons.
The active site of this enzyme contains a tightly bound zinc ion (\(Zn^{2+}\)) coordinated by three histidine residues.
This zinc ion acts as a strong Lewis acid, polarizing a bound water molecule to generate a nucleophilic hydroxide ion, which is essential for the catalytic mechanism. Thus, (A) is correct.
Phosphatase, Chymotrypsin, and Maltase: These enzymes do not require zinc as their primary, characteristic inorganic activator. For example, chymotrypsin is a serine protease that utilizes a catalytic triad (serine, histidine, aspartate) without requiring a metal ion, and maltase is a glucosidase that operates via acid-base catalysis.
Therefore, \(Zn^{2+}\) is the classic inorganic activator for carbonic anhydrase. Step 2: Final Answer:
The correct option is (A).
