title: Properties of the Na+, K+-stimulated adenosine triphosphatase system associated with the plasma membrane of pig thyroid glands.
abstract: The enzymatic properties of plasma membrane-bound Na+, K+-ATPase [EC 3.6.1.3], isolated with high specific activity and in good yield from pig thyroid cells, were examined. The enzyme activity required the presence of both Na+ and K+ at physiological concentrations; it exhibited high sensitivity to K+ and an absolute requirement for Na+. It showed highly specific requirement for Mg2+ and ATP. The apparent Km for ATP was 0.14 mM under the assay conditions. Arrhenius plots had a point of inflection at about 22 degrees C, activation energies being 24.2 kcal/mol at 5-22 degrees C and 19.0 kcal/mol at 22-40 degrees C. In addition to ouabain, the ATPase was strongly inhibited by fluoride and the SH-blocking reagent, PCMB. Iodide and TSH had no appreciable effect on the enzyme activity.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002413:Cations, Divalent; D002414:Cations, Monovalent; D002462:Cell Membrane / Q000201:enzymology; D002729:Chloromercuribenzoates / Q000494:pharmacology; D004789:Enzyme Activation; D005033:Ethylmaleimide / Q000494:pharmacology; D005459:Fluorides / Q000494:pharmacology; D007454:Iodides / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013552:Swine; D013696:Temperature; D013961:Thyroid Gland / Q000201:enzymology*
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D002729:Chloromercuribenzoates; D007454:Iodides; D010042:Ouabain; D012964:Sodium; D000251:Adenosine Triphosphatases; D008274:Magnesium; D005033:Ethylmaleimide; D005459:Fluorides; D011188:Potassium