Carbonic anhydrase 3 (CA3) is also known as Carbonate dehydratase III, Carbonic anhydrase III, which belongs to the alpha-carbonic anhydrase family. These carbonic anhydrases are a class of metalloenzymes that catalyze the reversible hydration of carbon dioxide and are differentially expressed in a number of cell types. The catalytic activity of carbonic anhydrase 3 is activated by proton donors such as imidazole and the dipeptide histidylhistidine and is inhibited by coumarins and sulfonamide derivatives such as acetazolamide.