Question

What is the coordination number of the metal ion in the active site of carbonic anhydrase, given its crystal structure and the ligands present?

Answer 1

Carbonic anhydrase is a metalloenzyme that contains a zinc ion  Zn2+  in its active site. The coordination number of the zinc ion in the active site of carbonic anhydrase is 4. This is because the zinc ion is coordinated to three histidine residues from the protein and a water molecule or hydroxide ion, depending on the state of the enzyme. The coordination geometry around the zinc ion is approximately tetrahedral.