Carbonic anhydrase II and IV isoenzymes (CA II and IV)

Carbonic anhydrase II (CA II) and Carbonic anhydrase IV (CA IV) are two distinct but functionally related zinc-containing metalloenzymes belonging to the carbonic anhydrase family. CA II is a highly active cytosolic enzyme found in various tissues like red blood cells, kidney, gastrointestinal tract, eye, and brain. CA IV, in contrast, is a membrane-anchored enzyme, localized on the luminal surface of epithelial and endothelial cells, particularly in the kidney and eye, where it regulates extracellular pH. Both isoenzymes catalyze the reversible hydration of carbon dioxide to bicarbonate and protons, a fundamental process for acid-base homeostasis. They possess high catalytic efficiencies and are critical therapeutic targets for multiple classes of clinically validated drugs, notably sulfonamide derivatives, used in conditions like glaucoma, epilepsy, and fluid retention disorders[1][2][3][4][5][6].

Other names

Carbonic anhydrase IICA2CA IICarbonic anhydrase 2 (gene product)HCA IICarbonic anhydrase IVCA4CA IVMembrane-associated carbonic anhydraseCA-IV

Inhibition of carbonic anhydrase isoenzymes, including both CA II and CA IV, underlies the therapeutic effects of various drugs. For instance, inhibition of CA II reduces the production of aqueous humor, thereby lowering intraocular pressure (used in glaucoma), and modulates neuronal excitability (contributing to anticonvulsant effects). Both CA II and CA IV inhibition promote renal bicarbonate excretion, leading to diuresis. Specifically, inhibition of membrane-associated CA IV decreases bicarbonate reabsorption and influences local pH microenvironments in the eye and kidney, contributing to the overall therapeutic actions of CA inhibitors.