Canadian Health&Care; Mall

The vacuolar-H+ATPase (V-ATPase) is a multisubunit enzyme that couples ATP hydrolysis to proton pumping across membranes. It is ubiquitously expressed in eukaryotic cells, where it participates in the acidification of highly differentiated organelles, including the Golgi apparatus, lysosomes, endo-somes, and secretory vesicles. In addition, the V-ATPase is also found at high density in the plasma membrane of specialized epithelial cells that are involved in active proton transport and pH regulation of extracellular compartments, such as narrow and clear cells in the epididymis and vas deferens, renal intercalated cells, osteoclasts, or some cell types in the inner ear, including interdental cells, which resemble renal intercalated cells. In the epididymis and proximal vas deferens, plasma membrane V-ATPase in narrow and clear cells is involved in the establishment of an acidic luminal pH that contributes to maintaining spermatozoa in a quiescent state during their maturation and storage in these organs. In the kidney, expression of the V-ATPase in the plasma membrane of collecting duct intercalated cells is critical for the regulation of systemic acid/base balance. In osteoclasts, the V-ATPase plays a vital role in bone resorption, and in the inner ear it is involved in maintaining the high K+ level of the endolymph that is essential for hearing.