University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Website: @unf

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Classification: Cell -> gastric

Citations 1

"A Continuous-flow Technique For Analysis Of Stoichiometry And Transport Kinetics Of Gastric Hydrogen Ion And Potassium-ATPase"
Acta Physiol. Scand. 1990 Volume 140, Issue 4 Pages 567-573
Norberg L, Mardh S.

Abstract: A continuous-flow method was developed for determining the stoichiometry of the gastric proton pump H,K-ATPase (EC in its hydrolysis of ATP and translocation of H+ and the K+ congener 86Rb+. H,K-ATPase-containing vesicles which had been isolated from pig gastric mucosa were incubated at 37°C for 2 h in 150 mM 86RbCl, 0.5 mM ethylenebis(oxyethylenenitrilo)tetra-acetic acid and 3 mM 2-(N-morpholino)ethane sulphonic acid (Mes) adjusted to pH 6.1 with Tris, and then applied onto a 0.45 micron pore size cellulose acetate filter. The immobilized vesicles were superfused with 0.15 mM Mes/Tris buffer, pH 6.1, containing 150 mM choline chloride and 0.2 mM MgCl2. After changing to a medium containing 0.1 mM ATP, the amounts and rates of H+ uptake, 86Rb+ efflux and ATP hydrolysis were measured. The initial ratio of Rb+ transported to ATP hydrolyzed gave values of 0.96±0.26 (mean±SD, n = 28). The initial ratio of ATP-dependent Rb+ efflux to H+ uptake gave values of 0.92±0.28 (mean±SD, n = 28). The Mg-ATPase activity was measured in vesicles which had been incubated with choline chloride instead of RbCl. This activity was 15.8±8.7% (mean±SD) of the total ATPase activity in the initial fractions used for calculation of the stoichiometry. It is argued that this Mg-ATPase may be an intrinsic activity of the H,K-ATPase and that the relation between these activities is dependent on the amount of K+ (or Rb+) present in the assay.
Hydrogen Hydrochloric acid Potassium ATP pH Enzyme, adenosine triphosphatase Stoichiometry Kinetic Enzyme