胃上皮细胞中与（Na⁺ + K⁺）转运ATP酶相关的钾离子刺激的对硝基苯磷酸酶活性的一半暴露于细胞表面外侧。
Half of the (Na+ + K+)-transporting-ATPase-associated K+-stimulated p-nitrophenyl phosphatase activity of gastric epithelial cells is exposed to the surface exterior.
作者信息
Nandi J, Das P K, Levine R A, Ray T K
机构信息
Department of Surgery, State University, New York Health Science Center, Syracuse 13210.
出版信息
Biochem J. 1988 May 15;252(1):29-34. doi: 10.1042/bj2520029.
Ouabain inhibited 86RbCl uptake by 80% in rabbit gastric superficial epithelial cells (SEC), revealing the presence of a functional Na+,K+-ATPase [(Na+ + K+)-transporting ATPase] pump. Intact SEC were used to study the ouabain-sensitive Na+,K+-ATPase and K+-pNPPase (K+-stimulated p-nitrophenyl phosphatase) activities before and after lysis. Intact SEC showed no Na+,K+-ATPase and insignificant Mg2+-ATPase activity. However, appreciable K+-pNPPase activity sensitive to ouabain inhibition was demonstrated by localizing its activity to the cell-surface exterior. The lysed SEC, on the other hand, demonstrated both ouabain-sensitive Na+,K+-ATPase and K+-pNPPase activities. Thus the ATP-hydrolytic site of Na+,K+-ATPase faces exclusively the cytosol, whereas the associated K+-pNPPase is distributed equally across the plasma membrane. The study suggests that the cell-exterior-located K+-pNPPase can be used as a convenient and reliable 'in situ' marker for the functional Na+,K+-ATPase system of various isolated cells under noninvasive conditions.
哇巴因抑制兔胃表层上皮细胞（SEC）对86RbCl的摄取达80%，这表明存在功能性钠钾ATP酶[（钠 + 钾）转运ATP酶]泵。完整的SEC用于研究裂解前后对哇巴因敏感的钠钾ATP酶和钾依赖对硝基苯磷酸酶（K + 刺激的对硝基苯磷酸酶）活性。完整的SEC未显示钠钾ATP酶活性，且镁离子ATP酶活性不显著。然而，通过将其活性定位到细胞表面外侧，证实了存在对哇巴因抑制敏感的可观的钾依赖对硝基苯磷酸酶活性。另一方面，裂解后的SEC显示出对哇巴因敏感的钠钾ATP酶和钾依赖对硝基苯磷酸酶活性。因此，钠钾ATP酶的ATP水解位点仅面向细胞质，而相关的钾依赖对硝基苯磷酸酶则均匀分布于质膜。该研究表明，位于细胞外侧的钾依赖对硝基苯磷酸酶可作为一种方便可靠的“原位”标记物，用于在非侵入性条件下研究各种分离细胞的功能性钠钾ATP酶系统。
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