title: A fluorometric assay for the potassium-dependent phosphatase activity of the (Na+ + K+)-adenosine triphosphatase.
abstract: A fluorometric assay for the K+-dependent phosphatase activity of the (Na+ + K+)-ATPase in both purified and membrane-bound forms is described. The assay utilizes 3-O-methylfluorescein phosphate as substrate and measures the fluorescence of the 3-O-methylfluorescein produced by hydrolysis of the substrate. The assay described is an order of magnitude more sensitive than the assay employing p-nitrophenylphosphate, the substrate most commonly used to measure this activity. The assay is also suitable for the specific measurement of (Na+ + K+)-ATPase activities in membranes which contain high levels of other ATPase activities.
authors.affiliation: CSIRO Division of Food Research, Meat Research Laboratory, Queensland, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Horgan
authors.forename: R
authors.initials: R
authors.lastname: Kuypers
mesh_terms: D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D006868:Hydrolysis; D007668:Kidney / Q000201:enzymology; D008565:Membrane Proteins / Q000032:analysis; D011188:Potassium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis*; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D008565:Membrane Proteins; C045349:3-O-methyl-fluorescein phosphatase; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium