Carbonic anhydrase 1; Carbonic anhydrase 2 (CA1; CA2)

Carbonic anhydrase 1 and carbonic anhydrase 2 are zinc-containing enzymes (metalloenzymes) that catalyze the rapid and reversible conversion of carbon dioxide and water to carbonic acid, protons, and bicarbonate ions. These enzymes are crucial for maintaining acid-base balance, facilitating carbon dioxide transport in the blood, and supporting physiological processes in tissues such as the kidney, eye, and gastrointestinal tract. CA1 is most abundant in erythrocytes, while CA2 has broad tissue distribution and is the most catalytically efficient human isoform. Targeted inhibition of these enzymes has substantial therapeutic relevance in glaucoma, edema, epilepsy, and other diseases associated with pH and fluid imbalance. Their active sites include a zinc ion coordinated by histidine residues and nearby amino acids critical for catalysis and inhibitor binding.

Other names

CA I (carbonic anhydrase I)CA II (carbonic anhydrase II)Carbonate hydro-lyaseEC 4.2.1.1 (Enzyme Commission number)

Most drugs are carbonic anhydrase inhibitors, typically binding the active site zinc or obstructing the catalytic turnover by occupying the substrate binding pocket or neighboring regions. Inhibition leads to decreased formation of bicarbonate ions and protons, with physiological effects such as reduced intraocular pressure (glaucoma) and promotion of renal excretion of sodium and water (diuretic effect).