Catalyzes the reversible hydration of carbon dioxide (PubMed:10550681, PubMed:18618712). Can hydrate cyanamide to urea (PubMed:10550681). H(+) + hydrogencarbonate = CO2 + H2O urea = cyanamide + H2O Activated by histamine, imidazole, L-adrenaline, L- and D-histidine, and L- and D-phenylalanine. Inhibited by coumarins, sulfonamide derivatives such as acetazolamide, benzenesulfonamide and derivatives (4-carboxyethylbenzene-sulfonamide, 4-carboxyethylbenzene-sulfonamide ethyl ester, 4-(acetyl-2-aminoethyl)benzene-sulfonamide, 4-aminoethylbenzene-sulfonamide), and 'prong inhibitors' BR15, BR17, BR22 and BR30. Activated by a short exposition to Foscarnet (phosphonoformate trisodium salt), but inhibited by a long one. Esterase activity weakly reduced by cyanamide. Belongs to the alpha-carbonic anhydrase family.