The protein, carbonic anhydrase IX, belongs to the carbonic anhydrase family which consists of enzymes that rapidly convert carbon dioxide and water into the end products of carbonic acid, protons, and bicarbonate ions. These enzymes play a widespread role in cells by regulating the pH of normal tissues, and are abundantly expressed in all mammalian tissues. Due to its stability and membrane location, CAIX is one of the most hypoxically-inducible genes, and has become a reliable hypoxia histochemical marker.
