Purification and characterization of (H++K+)-ATPase from hog gastric mucosa.

DOI PubMed 3 Citations
  • HONGO Toshio
    Department of Membrane Biology, Faculty of Pharmaceutical Sciences, Teikyo University
  • NOJIMA Shoshichi
    Department of Membrane Biology, Faculty of Pharmaceutical Sciences, Teikyo University
  • SETAKA Morio
    Department of Membrane Biology, Faculty of Pharmaceutical Sciences, Teikyo University

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Abstract

A (H++K+)-ATPase-enriched membrane fraction derived from the fundic portion of hog gastric mucosa was obtained by a combination of differential and repeated 7% Ficoll gradient centrifugation. The microsomal membrane fraction isolated by repeated 7% Ficoll gradient centrifugation was free of ouabain-sensitive (Na++K+)-ATPase, 5'-nucleotidase and succinate dehydrogenase; and it was highly enriched in (H++K+)-ATPase and K+-stimulated p-nitrophenylphosphatase (p-NPPase). The (H++K+)-ATPase had a pH optimum of 7.4 and was stimulated by Tl+, K+, Rb+ and NH4+ with Ka values of 0.0667, 0.526, 0.667 and 3.03 mM, respectively, at this pH. On the other hand, monovalent cations such as Na+, Li+ and (CH3)4N+ as well as divalent cations such as Cu2+, Ca2+, Ba2+, Sr2+ and Cd2+ inhibited this enzyme activity concentration-dependently. Ouabain and oligomycin had no effect, whereas omeprazole, a specific (H++K+)-ATPase inhibitor, inhibited this enzyme activity in a pH-dependent manner. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis showed a major band (≥=90% of protein) at 97, 400 daltons, which was phosphorylated in the presence of Mg2+ and [γ-32P]-ATP and dephosphorylated in the presence of K+. The present method was very simple, and the (H++K+)-ATPase activity of the microsomal fraction obtained by this method was much higher compared with those obtained by other methods such as free-flow electrophoresis.

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