Carbonic anhydrases (CAs) are enzymes which catalyze the reversible hydration of carbon dioxide according to the following reaction: CO2 + H2O ↔ HCO3- + H+
The main function of this protein family is to regulate the acid-base balance, which is of a considerable biological importance. In addition, they participate in several other physiological functions including CO2 and HCO3- transport, bone resorption, production of biological fluids, ureagenesis, gluconeogenesis, and lipogenesis. Carbonic anhydrases are metalloenzymes containing a zinc-atom in their active site. The expanding CA gene family includes at least 13 enzymatically active members with different structural and catalytic properties. Each isoform has a characteristic distribution in tissues. CA II , IX and XII are expressed in a number of malignant tissues. Based on the distribution and functional studies, they may play a role in neoplastic processes such as invasion and increased cell proliferation.