Human carbonic anhydrases: Tissue distribution, physiological role, and druggability

Fifteen different carbonic anhydrase (CA) isoforms have been identified and characterized in human (h) so far, of which 12 are catalytically active and 3 lack activity (CA-related proteins). hCAs differ by molecular features, oligomeric arrangement, cellular localization, distribution in organs and tissues, expression levels, kinetic properties, and response to different classes of inhibitors. By catalyzing the reversible hydration of CO2 to and proton, hCAs are involved in a plethora of physiological processes, such as gas exchange, transport of CO2 and across membranes, biosynthetic reactions, acid-base tuning, and calcification. Abnormal levels or activities of these enzymes have been associated to a number of human diseases resulting in an increasing interest of the scientific community for the design of hCA inhibitors or activators with biomedical applications.