Purification and characterization of (H++K+)-ATPase from hog gastric mucosa.
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概要
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A (H<SUP>+</SUP>+K<SUP>+</SUP>)-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<SUP>+</SUP>+K<SUP>+</SUP>)-ATPase, 5'-nucleotidase and succinate dehydrogenase; and it was highly enriched in (H<SUP>+</SUP>+K<SUP>+</SUP>)-ATPase and K<SUP>+</SUP>-stimulated p-nitrophenylphosphatase (p-NPPase). The (H<SUP>+</SUP>+K<SUP>+</SUP>)-ATPase had a pH optimum of 7.4 and was stimulated by Tl<SUP>+</SUP>, K<SUP>+</SUP>, Rb<SUP>+</SUP> and NH<SUB>4</SUB><SUP>+</SUP> 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<SUP>+</SUP>, Li<SUP>+</SUP> and (CH<SUB>3</SUB>)<SUB>4</SUB>N<SUP>+</SUP> as well as divalent cations such as Cu<SUP>2+</SUP>, Ca<SUP>2+</SUP>, Ba<SUP>2+</SUP>, Sr<SUP>2+</SUP> and Cd<SUP>2+</SUP> inhibited this enzyme activity concentration-dependently. Ouabain and oligomycin had no effect, whereas omeprazole, a specific (H<SUP>+</SUP>+K<SUP>+</SUP>)-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 Mg<SUP>2+</SUP> and [γ-<SUP>32</SUP>P]-ATP and dephosphorylated in the presence of K<SUP>+</SUP>. The present method was very simple, and the (H<SUP>+</SUP>+K<SUP>+</SUP>)-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.
- 公益社団法人 日本薬理学会の論文