Carbonic anhydrase is an example of:

Metalloenzymes:  These enzymes hold the metals rather tightly which are not readily exchanged. e.g., alcohol dehydrogenase, carbonic anhydrase, alkaline phosphatase, carboxypeptidase and aldolase contain zinc. Phenol oxidase (copper) Pyruvate oxidase (manganese) Xanthine oxidase (molybdenum) Cytochrome oxidase (iron and copper) Key Concept: Metalloproteins: They contain metal ions. Examples are Hemoglobin (Iron), Cytochrome (Iron), Tyrosinase (Copper) and Carbonic anhydrase (Zinc). Ref : Textbook of Biochemistry, Satyanarayana