scholarly journals Differential effects of lipid depletion on membrane sodium-plus-potassium ion-dependent adenosine triphosphatase and potassium ion-dependent phosphatase

1975 ◽  
Vol 146 (3) ◽  
pp. 723-727 ◽  
Author(s):  
K P Wheeler ◽  
J A Walker
Keyword(s):  
Phosphatase Activity ◽  
Differential Effect ◽  
Adenosine Triphosphatase ◽  
Total Phospholipid ◽  
Potassium Ion ◽  
Single Extraction ◽  
Phosphatase Activities ◽  
Dependent Atpase ◽  
Atpase System ◽  
Lipid Requirement

The phospholipid-dependence of the (Na-++K-+)-dependent ATPase (adenosine triphosphatase) (EC 3.6.1.3) and associated K-+-dependent phosphatase activity (EC 3.6.1.7) have been compared. Unlike the (Na-++K-+)-dependent ATPase activities, the K-+-dependent phosphatase activities of a number of different preparations were not closely correlated with their total phospholipid contents. After partial lipid depletion with a single extraction in Lubrol W the residual ATPase and phosphatase activities were correlated, but their magnitudes were quite different: on average only about 5% of the former remained compared with 50% of the latter. A similar differential effect on these activities was found after extraction with deoxycholate. In contrast with the ATPase, consistent restoration of the phosphatase activity of Lubrol-extracted enzymes by added exogenous phospholipids was not observed. We conclude that, although the K-+-dependent phosphatase may be lipid-dependent, the lipid requirement must be different from that of the complete ATPase system, and this difference should help investigations of their relationship.

scholarly journals Role of phospholipid in the intermediate steps of the sodium-plus-potassium ion-dependent adenosine triphosphatase reaction

1975 ◽  
Vol 146 (3) ◽  
pp. 729-738 ◽  
Author(s):  
K P Wheeler
Keyword(s):  
Phosphatase Activity ◽  
Adenosine Triphosphatase ◽  
Atp Hydrolysis ◽  
Reaction Sequence ◽  
Single Extraction ◽  
Background Value ◽  
Dependent Atpase ◽  
Membrane Atpase ◽  
Normal Enzyme

The phosphorylation and dephosphorylation steps of the (Na-++K-+)-dependent ATPase (adenosine triphosphatase) (EC 3.6.1.3) reaction have been compared in ‘normal’, lipid-depleted and ‘restored’ membrane ATPase preparations. Partial lipid depletion was achieved by a single extraction with Lubrol W, and ‘restoration’ by adding pure phosphatidylserine. γ-32-P-labelled ATP was used for phosphorylation. The main findings were as follows. (1) Partial lipid depletion decreased but did not prevent Na-+-dependent phosphorylation, although it virtually abolished both Na-+-dependent and (Na-++K-+)-dependent ATPase activities. (2) ‘Restoration’ with phosphatidylserine produced an increment in phosphorylation that was the same in the presence and absence of added Na-+. (3) K-+ decreased the extent of Na-+-dependent phosphorylation of the depleted enzyme without producing a corresponding release of Pi. (4) K-+ rapidly decreased the extent of phosphorylation of the ‘restored’ enzyme to near-background value, with a concomitant release of Pi. (5) Na-+-dependent ATP hydrolysis was not restored. (6) The turnover of the ‘restored’ enzyme seemed to be higher than that of the ‘normal’ enzyme. The reaction sequence is discussed in relation to these results and the fact that the depleted enzyme retained about 50% of K-+-dependent phosphatase activity.

scholarly journals Calcium ion-dependent p-nitrophenyl phosphate phosphatase activity and calcium ion-dependent adenosine triphosphatase activity from human erythrocyte membranes

1973 ◽  
Vol 136 (1) ◽  
pp. 185-194 ◽  
Author(s):  
Alcides F. Rega ◽  
Donaldo E. Richards ◽  
Patricio J. Garrahan
Keyword(s):  
Cell Membrane ◽  
Phosphatase Activity ◽  
Human Erythrocyte ◽  
Calcium Ion ◽  
Adenosine Triphosphatase ◽  
Erythrocyte Membranes ◽  
Dependent Atpase ◽  
Nitrophenyl Phosphate ◽  
Inner Surface ◽  
Human Erythrocyte Membranes

In the presence of ATP and of Mg2+, human erythrocyte membranes show a phosphatase activity towards p-nitrophenyl phosphate which is activated by low concentrations of Ca2+. The effect of Ca2+ is strongly enhanced if either K+ or Na+ is also present. Activation of the p-nitrophenyl phosphate phosphatase by Ca2+ reaches a half-maximum at about 8μm-Ca2+ and is apparent only when the ion has access to the inner surface of the cell membrane. Ca2+-dependent phosphatase activity can only be observed if ATP is at the inner surface of the cell membrane, and the presence of ATP seems to be absolutely necessary, since either its removal or its replacement by other nucleoside triphosphates abolishes the activating effect of Ca2+. The properties of the (ATP+Ca2+)-dependent phosphatase are very similar to those of the Ca2+-dependent ATPase (adenosine triphosphatase), also present in erythrocyte membranes, which probably is involved in Ca2+ transport in erythrocytes. The similarities suggest that both activities may be properties of the same molecular system. This view is further supported by the fact that p-nitrophenyl phosphate inhibits to a similar extent Ca2+-dependent ATPase activity and ATP-dependent Ca2+ extrusion from erythrocytes.

scholarly journals Differential effects of temperature on a membrane adenosine triphosphatase and associated phosphatase

1975 ◽  
Vol 151 (2) ◽  
pp. 439-442 ◽  
Author(s):  
J A Walker ◽  
K P Wheeler
Keyword(s):  
Atpase Activity ◽  
Phosphatase Activity ◽  
Adenosine Triphosphatase ◽  
Arrhenius Plots ◽  
Differential Effects ◽  
Adenosine Triphosphatase Activity ◽  
Dependent Atpase ◽  
Effects Of Temperature

Arrhenius plots of a membrane (Na+ + K+)-dependent ATPase (adenosine triphosphatase) activity showed characteristic discontinuities, whereas those of the associated K+-dependent phosphatase activity did not. These findings support the contention that the phosphatase activity does not depend on phospholipid in the same way as does the ATPase activity.

scholarly journals No major thermogenic role for (Na+ + K+)-dependent adenosine triphosphatase apparent in hepatocytes from hyperthyroid rats

1982 ◽  
Vol 202 (3) ◽  
pp. 661-665 ◽  
Author(s):  
D G Clark ◽  
M Brinkman ◽  
O H Filsell ◽  
S J Lewis ◽  
M N Berry
Keyword(s):  
Oxygen Consumption ◽  
Oxygen Uptake ◽  
Atpase Activity ◽  
Heat Production ◽  
Adenosine Triphosphatase ◽  
Heat Output ◽  
Liver Parenchymal ◽  
Dependent Atpase ◽  
Parenchymal Cells ◽  
Isolated Liver

(Na+ + K+)-dependent ATPase activity, heat production and oxygen consumption were increased by 59%, 62% and 75% respectively in hepatocytes from tri-iodothyronine-treated rats. Ouabain at concentrations of 1 and 10 mM decreased oxygen uptake by 2-8% in hepatocytes from euthyroid rats and by 5-15% in hepatocytes from hyperthyroid animals. Heat output was decreased by 4-9% with the glycoside in isolated liver parenchymal cells from the control animals and by 11% in the cells from the tri-iodothyronine-treated animals. These results do not support the hypothesis that hepatic (Na+ + K+)-ATPase plays a major role in increased heat production in hepatocytes from hyperthyroid rats.

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