Which enzyme cofactor is an inorganic zinc ion () tightly coordinated to three histidine residues in the active site?
Answer and explanation
Correct answer: B. Carbonic anhydrase
- Step 1: Carbonic anhydrase catalyzes the reversible interconversion of carbon dioxide and water into bicarbonate: .
- Step 2: It is one of the fastest known enzymes, with a turnover number of .
- Step 3: Its catalytic mechanism depends on an essential ion coordinated in the active site that polarizes water to generate a reactive hydroxide nucleophile.
Answer
Carbonic anhydrase.
Why not the others: Catalase requires an iron-heme prosthetic group; Peroxidase requires an iron-heme group; Hexokinase uses as a cofactor to coordinate ATP.
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