Reversible hydration of carbon dioxide. H(+) + hydrogencarbonate = CO2 + H2O Inhibited by coumarins, sulfonamide derivatives such as acetazolamide (AZA) and Foscarnet (phosphonoformate trisodium salt). Expressed in spleen, lung, kidney, heart, brain, skeletal muscle and testis. Belongs to the alpha-carbonic anhydrase family.