Potassium Hydrogen ATPase (H⁺/K⁺-ATPase)

Potassium hydrogen ATPase (H⁺/K⁺-ATPase) is a membrane-bound enzyme complex primarily responsible for the acidification of the stomach contents by exchanging intracellular protons (H⁺) for extracellular potassium ions (K⁺), using energy derived from ATP hydrolysis. It is a P-type ATPase found predominantly in the gastric parietal cells of the stomach lining, with isoforms also present in renal tissue. The functional enzyme consists of two subunits: a large α-subunit (~100 kDa) containing the catalytic site and ion translocation pathways, and a smaller, glycosylated β-subunit (~30 kDa) required for proper folding, trafficking, and stability. It catalyzes an electroneutral exchange of one proton for one potassium ion. It is indirectly activated by gastrin via histamine release and is targeted by proton pump inhibitors (PPIs) to treat acid-related disorders.

Other names

Hydrogen potassium ATPaseGastric proton pump

Proton pump inhibitors (PPIs) covalently bind cysteine residues on the luminal-facing domains of the α-subunit, irreversibly inhibiting acid secretion.