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.