H+/K+-ATPase (gastric proton pump)

Class

Proton pump inhibitor (PPI)

Pathway

Gastric acid secretion pathway — irreversibly inhibits the parietal cell proton pump

The gastric H+/K+-ATPase, often called the proton pump, is an enzyme located on the surface of parietal cells lining the stomach. Its function is to exchange potassium ions for hydrogen ions across the cell membrane, and this hydrogen ion secretion is the final, common step by which the stomach acidifies its contents, regardless of what upstream signal (histamine, gastrin, or acetylcholine) triggered acid release. Because it sits at the end of this pathway, blocking the pump provides a highly effective way to reduce gastric acidity irrespective of which stimulus is driving secretion. Proton pump inhibitors bind to and irreversibly inactivate this enzyme, so acid output only recovers once the parietal cell synthesizes new pump molecules. This mechanism broadly matters in conditions where excess or poorly controlled acid damages tissue: gastroesophageal reflux disease, peptic ulcers, and states of pathological acid hypersecretion. It is also used to protect the stomach lining when other medications, such as certain anti-inflammatory drugs, increase ulcer risk. Because the pump is specific to the acid-secreting mechanism of parietal cells, this class of therapy achieves potent, sustained suppression of acid production with a mechanism distinct from earlier drugs that only blocked a single upstream receptor.