title: Lead actions on sodium-plus-potassium-activated adenosinetriphosphatase from electroplax, rat brain, and rat kidney.
abstract: Inorganic lead ion, in micromolar concentrations, reversibly inhibits the sodium-plus-potassium-activated adenosinetriphosphatase (ATPase) and potassium-activated p-nitrophenylphosphatase (NPPase) activities of microsomal fractions from electric organ, rat kidney, and rat brain. In the presence of 3 mM MgC12 and 3 mM ATP, the concentrations of PbC12 producing half-maximal inhibition of the ATPase from these tissues are 4 X 10(-6) M, 20 X 10(-6) M, and 55 X 10(-6) M, respectively. The corresponding values for inhibition of the NPPase are 10(-6) M, 53 X  10(-6) M, and 22 X 10(-6) M. PbC12 also stimulates the phosphorylation by [gamma-32P]ATP of a microsomal protein from all three tissues in the absence of added sodium ion. This reaction was extensively studied with electroplax microsomes. In common with the well-known Na+-dependent phosphorylation of (Na+ + K+)-ATPase, the Pb2 -dependent reaction is inhibited by ouabain, specific for ATP, dependent on Mg2+, and yields and acid-stable phosphoprotein with a molecular weight of 98,000 in sodium dodecylsulfate. The Pb2+-dependent phosphoprotein, however, is not sensitive to K+. These observations are pertinent to the biochemistry and toxicity of inorganic lead in tissues and to the molecular mechanism of the cation transport enzyme.
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000037:antagonists & inhibitors; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D004557:Electric Organ / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D005399:Fishes; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D007700:Kinetics; D007854:Lead / Q000494:pharmacology*; D008861:Microsomes / Q000201:enzymology; D010750:Phosphoproteins / Q000096:biosynthesis; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism
chemical_list: D010750:Phosphoproteins; D007854:Lead; D012964:Sodium; D009597:4-Nitrophenylphosphatase; D000251:Adenosine Triphosphatases; D011188:Potassium