Modulation of gastric H+, K+‐transporting ATPase function by sodium
- 3 June 1985
- journal article
- Published by Wiley in FEBS Letters
- Vol. 185 (1) , 24-28
- https://doi.org/10.1016/0014-5793(85)80733-x
Abstract
Gastric H+, K+‐ATPase activity is not affected by Na+ at pH 7.0 but is significantly stimulated by Na+ at pH 8.5. For the stimulation at the latter pH, the presence of both Na+ and K+ were essential. Contrary the H+, K+‐ATPase, the associated K+‐pNPPase was inhibited by Na+ at both pH values. Sodium competes with K+ for the K+‐pNPPase reaction. Also, unlike the H+, K+‐ATPase activity the ATPase‐mediated transport of H+ within the gastric microsomal vesicles was inhibited by Na+. For the latter event only the extravesicular and not the intravesicular Na+ was effective. The data suggest that the K+‐pNPPase activity does not represent the phosphatase step of the H+, K+‐ATPase reaction. In addition, the observed inhibition of vesicular H+ uptake by Na+ appears to be due to the displacement by Na+ of a cytosolic (extravesicular) H+ site responsible for the vectorial translocation of H+Keywords
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