CA3, also known as carbonic anhydrase III, is an enzyme that catalyses rapid conversion of carbon dioxide to bicarbonate and protons (CO2 + H2O = HCO3 + H+). This protein is involved in a variety of biological processes, including respiration, calcifica-tion, acid-base balance, bone resorption and the formation of aqueous humor, cerebrospinal fluid, saliva and gastric juice. It contains a zinc ion in their active site and the primary function of this enzyme is known to maintain acid-base balance in blood and other tissues, and to help transport carbon dioxide of tissues. Recombinant CA3 protein was expressed in E.coli and purified by using conventional chromatography techniques. Synonyms: CAIII, Car3, Carbonic anhydrase III, CA3,. NCBI no.: AAH04897