Carbonic Anhydrase II (CA2) is one of the 14 isoforms of the carbonic anhydrase enzyme, which are zinc containing enzymes that catalyze the reversible hydration of carbon dioxide to form bicarbonate and hydrogen ions. The major function of CA2 is in the proximal tubules of the kidney, where it is involved in bicarbonate reabsorption and distal renal tubular acidification. In addition, it also plays a major role in bone resorption by facilitating the production of hydrogen ions by osteoclasts.
Mutations in CA2 result in autosomal recessive osteopetrosis 3 characterized by renal tubular acidosis, cerebral calcification, and abnormally dense and brittle bones.