Question

The metal ion present in human carbonic anhydrase is

• A. Fe³⁺
• B. Cu²⁺
• C. Zn²⁺
• D. Ni²⁺

Answer 1

The Correct Option is C

The question asks about the metal ion present in human carbonic anhydrase, an enzyme that catalyzes the reversible hydration of carbon dioxide. Let's explore the options:

• Option A: Fe³⁺ - Iron ions are found in several enzymes but not commonly associated with carbonic anhydrase.
• Option B: Cu²⁺ - Copper ions are typically found in enzymes involved in electron transfer processes and are not relevant for carbonic anhydrase.
• Option C: Zn²⁺ - Zinc ions play a crucial role in the structure and function of carbonic anhydrase by acting as a cofactor that stabilizes the enzyme’s active site.
• Option D: Ni²⁺ - Though nickel can be a catalytic metal ion in some enzymes, it is not the metal ion used by carbonic anhydrase.

Among these choices, the correct answer is Zn²⁺. Human carbonic anhydrase specifically relies on zinc ions for its enzymatic activity. The presence of Zn²⁺ facilitates the conversion of carbon dioxide and water to bicarbonate and protons, a reaction essential for many physiological processes.

The structure of carbonic anhydrase includes a zinc ion bound at its active site, coordinated to three histidine residues and a water molecule/hydroxide ion. This specific metal coordination is critical for its catalytic function.

The answer is Zn²⁺, which is essential for the enzyme's activity by stabilizing the transition state and facilitating the conversion of CO₂ into bicarbonate.