Carbonic anhydrases (CAs) are a largefamily of zinc metalloenzymes first discovered in 1933 that catalyze thereversible hydration of carbon dioxide. CAs participate in a variety ofbiological processes, including respiration, calcification, acid-base balance,bone resorption, and the formation of aqueous humor, cerebrospinal fluid,saliva, and gastric acid. Carbonic anhydrases (CAs) form a family of enzymesthat catalyze the rapid conversion of carbon dioxide and water to bicarbonateand protons, a reaction that occurs rather slowly in the absence of a catalyst.The active site of most carbonic anhydrases contains a zinc ion, they aretherefore classified as metalloenzymes. Several forms of carbonic anhydraseoccur in nature. The primary function of the enzyme in animals is tointerconvert carbon dioxide and bicarbonate to maintain acid-base balance inblood and other tissues, and to help transport carbon dioxide out of tissues.Plants contain a different form called β-carbonic anhydrase, which, from anevolutionary standpoint, is a distinct enzyme, but participates in the samereaction and also uses a zinc ion in its active site.Carbonic anhydrase 3, also known asCarbonate dehydratase III, CA-III and CA3, is a cytoplasm protein which belongsto thealpha-carbonic anhydrase family. CA3 is activated by proton donorssuch as imidazole and the dipeptide histidylhistidine. It is inhibited bycoumarins and sulfonamide derivatives such as acetazolamide. At 6 weeksgestation, transcripts accumulate at low levels in the somites and at highlevels throughout the notochord. As gestation continues, CA3 becomes abundantin all developing muscle masses and continues at high to moderate levels in thenotochord.

carbonic anhydrase III