Carbonic Anhydrase

As zinc metalloenzymes, carbonic anhydrases catalyze the reversible hydration of carbon dioxide to bicarbonate and a proton, supporting pH homeostasis, ion transport, and fluid secretion across tissues. The human alpha-carbonic anhydrase isoforms (CA I through CA XIV) differ markedly in localization: CA I and II are cytosolic, CA IV is membrane-tethered, and CA IX and XII sit on the surface of hypoxic and tumor cells. Elevated CA IX expression marks aggressive solid tumors, and CA inhibitors such as acetazolamide are established drugs for glaucoma and altitude sickness. Recombinant carbonic anhydrases are widely used in inhibitor screening and enzymology.