title: The localization of (Ca2+ or Mg2+)-ATPase in plasma membranes of renal proximal tubular cells.
abstract: Basolateral and brush-border vesicles from pig kidney cortex were prepared by differential centrifugation followed by free-flow electrophoresis. A low-affinity (Ca2+ or Mg2+)-ATPase which co-migrated with alkaline phosphatase was demonstrated. A considerable enrichment (by a factor of 10) of this ATPase activity was only observed in the brush-border and not in the basolateral membrane fractions. Maximal stimulation of this brush-border enzyme by Ca2+ was achieved when the ratio of Ca2+ to ATP reached a value between 1 and 2. The enzyme was not inhibited by excess Ca2+ or Mg2+. A kinetic analysis of the azide-insensitive (Ca2+ or Mg2+)-ATPase gave a Km of 0.43 mM for Ca-ATP and of 0.14 mM for Mg-ATP.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001485:Basement Membrane / Q000201:enzymology; D017301:Ca(2+) Mg(2+)-ATPase / Q000032:analysis*; D000252:Calcium-Transporting ATPases / Q000032:analysis* / Q000378:metabolism; D007672:Kidney Cortex / Q000201:enzymology; D007687:Kidney Tubules, Proximal / Q000201:enzymology* / Q000648:ultrastructure; D007700:Kinetics; D008854:Microscopy, Electron; D008871:Microvilli / Q000201:enzymology; D013552:Swine
chemical_list: D000255:Adenosine Triphosphate; D000469:Alkaline Phosphatase; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases