Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Isolation of non-esterified [14C]cholesterol bound to albumin from rat serum, 8 days after i.p. injection of [14C]cholesterol, was achieved by affinity chromatography, using Cibacron blue F3GA bound to Sepharose 4B and by Sephadex G-150 column chromatography. Both methods permit isolation of large quantities of cholesterol-loaded albumin, free of globulins and lipoproteins. The isolated albumin-cholesterol fraction was estimated to be 4.6 mg/100 ml serum, which represents approx. the 24% of the non-esterified cholesterol present in the rat serum. Albumin-cholesterol, cholesterol glucoside, cholesterol hemisuccinate and hydroxylated derivatives of cholesterol produced a biphasic curve of changes in synaptosomal plasma membranes (SPM)-bound (Na+ + K+)-stimulated ATPase activity. Low concentrations of the ligand progressively increased the enzyme activity, while increasing the ligand concentration above that which maximally stimulated the enzyme activity, produced a progressive inhibition. Lipoproteins did not have any effect on the enzyme activity. The fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene-labeled SPM, increased in albumin-cholesterol derivatives-treated SPM, which is consistent with a general decrease in membrane bilayer fluidity. The results provide evidence that the 'albumin-cholesterol' fraction of the serum may directly affect the cell membrane-bound enzyme activity.
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PMID:Evidence for the existence of non-esterified cholesterol carried by albumin in rat serum. 301 57

The Na,K-ATPase partially purified from porcine lens fiber cells (Sen and Pfeiffer, 1982) is stimulated fourfold (specific activity) by treatment with sodium thiocyanate. The optimum conditions are 1.5 M NaSCN, 2 mg protein ml-1 reaction mixture, pH 7.0, with incubation continued for 30 min at 23 degrees C. Sodium docecyl sulphate-gel electrophoresis and [3H]ouabain binding studies indicate that the extent of purity is not increased significantly by the procedure. The high-activity preparation has elevated phospholipid:protein and phosphatidylethanolamine:sphingomyelin ratios compared with the deoxycholate-extracted starting material. The cholesterol:phospholipid ratio and phospholipid acyl group composition are not significantly altered by SCN- treatment. Measurements of 1,6-diphenyl-1,3,5-hexatriene fluorescence polarization show that SNC- treatment produces approximately a 5 degrees C decrease in a membrane phase transition temperature. The phase transition also affects the activation energy of the Na,K-ATPase reaction and probably reflects the onset of the gel to liquid crystalline transition rather than the midpoint location of the transition per se. p-Nitrophenylphosphatase activity and Na,K-ATPase activity in the gel state membrane are also increased by SCN- treatment. Increased specific activity may result, in part, from a membrane fluidity-dependent enzyme activation but is also due, in part, to the expression of latent enzyme activity. Using ouabain-binding data and the specific activity of the activated preparation, it can be shown that the turnover number of the fiber cell enzyme is approximately 1% of that observed in most other tissues.
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PMID:Persistent stimulation of lens fiber cell Na,K-ATPase by sodium thiocyanate. 302 21

Adriamycin (ADR) increased the lipid fluidity of dog brain synaptosomal plasma membranes (SPM) labeled with 1,6-diphenyl-1,3,5-hexatriene (DPH), as indicated by the steady-state fluorescence anisotropy [(ro/r)-1]-1. Arrhenius-type plots of [(ro/r)-1]-1 indicated that the lipid phase separation of the membrane at 23.3 +/- 1.2 degrees was perturbed by ADR such that the temperature was reduced to 16.2 +/- 1.1 degrees. Arrhenius plots of (Na+ + K+)-stimulated ATPase activity exhibited a break point at 22.8 +/- 1.1 degrees in control SPM which was reduced to 15.8 +/- 1.0 degrees in ADR treated SPM, suggesting differences in the interaction of (Na+ + K+)-stimulated ATPase with lipids between ADR treated and untreated SPM. (Na+ + K+)-stimulated ATPase and Ca2+-stimulated ATPase activities were increased at a concentration range 10(-18)-10(-15) M of ADR; higher concentrations (up to 10(-7) M), however, led to a progressive inhibition of the enzyme activities. The allosteric properties of SPM-bound (Na+ + K+)-stimulated ATPase by fluoride (F-) (as reflected by changes in the Hill coefficient) were modulated by ADR whereas those of SPM-bound acetylcholinesterase remained unaffected. We propose that ADR achieves these effects through asymmetric perturbations of the membrane lipid structure and that changes in membrane fluidity may be an early key event in ADR induced neurotoxicity.
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PMID:Evaluation of membrane fluidity effects and enzyme activities alterations in adriamycin neurotoxicity. 303 5

Na+:H+ and Cl-:HCO3- exchange are localized, respectively, to basolateral (blLPM) and canalicular (cLPM) rat liver plasma membranes. To determine whether these exchangers play a role in bile formation, we examined the effect of a choleretic agent, ursodeoxycholate (UDCA), on these exchange mechanisms. 22Na (1 mM) and 36Cl (5 mM) uptake was determined using outwardly directed H+ and HCO3- gradients, respectively. Preincubation of blLPM vesicles with UDCA (0-500 microM) resulted in a concentration-dependent increase in initial rates of amiloride-sensitive pH-driven Na+ uptake, with a maximal effect at 200 microM. UDCA (200 microM) increased Vmax from 23 +/- 2 (control) to 37 +/- 7 nmol/min per mg protein; apparent Km for Na+ was unchanged. Preincubation with tauroursodeoxycholate (200 microM), taurocholate (10-200 microM) or cholate, chenodeoxycholate, or deoxycholate (200 microM) had no effect on pH-driven Na+ uptake. UDCA (200 microM) had no effect on either membrane lipid fluidity, assessed by steady-state fluorescence polarization using the probes 1,6-diphenyl-1,3,5-hexatriene, 12-(9-anthroyloxy) stearic acid, and 2-(9-anthroyloxy) stearic acid (2-AS), or Na+,K+-ATPase activity in blLPM vesicles. In cLPM vesicles, UDCA (0-500 microM) had no stimulatory effect on initial rates of HCO3(-)-driven Cl- uptake. Enhanced basolateral Na+:H+ exchange activity, leading to intracellular HCO3- concentrations above equilibrium, may account for the bicarbonate-rich choleresis after UDCA infusion.
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PMID:Ursodeoxycholate stimulates Na+-H+ exchange in rat liver basolateral plasma membrane vesicles. 304 Aug 5

Rats were maintained on nutritionally complete diets enriched in unsaturated (corn oil) or saturated (butter fat) triacylglycerols. After 6 weeks, significant differences in the lipid composition and fluidity of a number of intestinal membranes were observed. The corn oil diet (enriched mainly in linoleic acid) increased the overall unsaturation of the acyl chains and enhanced the lipid fluidity, as assessed by the fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene, of enterocyte microvillus and basolateral membranes and of colonocyte basolateral membranes. Concomitantly, the cholesterol content and the cholesterol/phospholipid molar ratio were increased in the microvillus but not in the basolateral membranes. The increased cholesterol in ileal microvillus membranes can result from enhanced cellular biosynthesis, since ileal slices from rats fed the unsaturated diet incorporated [14C]octanoate more rapidly into digitonin-precipitable sterol. Increased fluidity of the enterocyte microvillus and basolateral membranes, respectively, enhanced the enzyme specific activities of p-nitrophenylphosphatase and (Na+ + K+)-dependent adenosine triphosphatase. The results indicate that the lipid composition, fluidity and enzyme activities of intestinal plasma membranes can be altered by dietary means. Moreover, rat enterocytes possess regulatory mechanisms which modulate the cholesterol content of the microvillus membranes so as to mitigate changes in lipid fluidity.
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PMID:Variations in dietary triacylglycerol saturation alter the lipid composition and fluidity of rat intestinal plasma membranes. 396 22

Human skin fibroblasts were taken from age-matched male and female subjects. The cells were then cultured under identical conditions and passage-number matched. Plasma membranes were isolated and membrane enzyme activities, lipid composition, and structure of isolated plasma membranes were measured in order to determine the presence of significant sex differences in human fibroblast membrane properties. The results indicated that plasma membranes from normal female subjects had a 1.6-fold and 3.6-fold higher cholesterol/phospholipid ratio and oleic acid (18:2) content than normal male subjects. The limiting anisotropy and the rotational relaxation time of fluorescence probe molecules such as trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene in the plasma membranes was not significantly different from fibroblasts of male versus female normal subjects. The total activity of plasma membrane (Na+, K+)-ATPase was significantly higher in female than male normal subjects. A potential 'membrane structural disorder', Huntington's disease, was confirmed in fibroblast membranes from male but not from female Huntington's disease subjects. The possibility that Huntington's disease was a 'premature membrane aging' phenomenon was considered. A comparison of plasma membrane enzymes, lipids, and structure from old and young Huntington's disease subjects did not show differences consistent with accelerated membrane aging as explaining the molecular basis for the disease. The age-dependent differences noted in aged Huntington's disease subjects: increased phosphatidylcholine/phosphatidylethanolamine ratio and sphingomyelin + lysophosphatidylcholine content of fibroblast plasma membranes were not significantly altered when compared to normal age-matched controls. However, (Na+, K+)-ATPase activity was significantly enhanced in fibroblast plasma membranes of older Huntington's disease subjects unlike those of control subjects. In conclusion, sex and age differences in membrane properties of cultured cells represent important potential variables in the elucidation of human genetic disorders that may be membrane-related.
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PMID:Sex and age alter plasma membranes of cultured fibroblasts. 608 40

Inhibition of renal Na+,K+-adenosine triphosphatase is an early biochemical manifestation of gentamicin treatment in rats. Studies with isolated, perfused rat kidneys in filtering and nonfiltering modes indicate that gentamicin is transported across the brush border membrane before enzyme inhibition. The drug caused enzyme inhibition (42%) only in filtering kidneys, and this inhibition was blocked by spermine, an inhibitor of gentamicin binding. In purified rat renal basolateral membranes, bound [3H]gentamicin was displaced 88% by unlabeled gentamicin. After in vivo exposure to [3H]gentamicin, the radioactivity associated with the isolated basolateral membranes was displaced only 46% by unlabeled drug. These results suggest that inhibition of renal Na+,K+-adenosine triphosphatase by gentamicin is probably due to an interaction at the cytoplasmic face of the basolateral membrane. Scatchard plots of [3H]gentamicin binding to basolateral and brush border membranes revealed a single class of noninteracting sites in each membrane. Gentamicin did not change the bulk membrane lipid fluidity, as estimated by the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene.
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PMID:Inhibition of renal Na+, K+-adenosine triphosphatase by gentamicin. 609 9

The effect of nitrogen mustard (2-chloro-N-2-chloroethyl-N-methylethanamine), Trenimon (2,3,5-trisethyleneiminobenzoquinone-1,4), chlorambucil (4-[p-(bis[2-chloroethyl]amino)-phenyl]butyric acid) and phosphamide mustard (N,N-bis(2-chloroethyl)-diamidophosphoric acid) on Na+/K+-ATPase, membrane fluidity and cell multiplication was studied. With the exception of chlorambucil which does not affect Na+/K+-ATPase all concentrations of the other alkylating agents which inhibit cell multiplication of Ehrlich ascites tumor cells depress the activity of the Na+/K+-ATPase. All alkylating agents--including chlorambucil--caused an increase in the apparent degree of fluorescence polarization after labelling of the plasma membrane with 1,6-diphenyl-1,3,5-hexatriene (DPH). This effect is interpreted as a decrease in membrane fluidity caused by the alkylating drugs. The decrease in membrane fluidity is due to a direct interaction of the alkylating agent with the plasma membrane and is expressed at all concentrations of the drug which inhibit cell proliferation. No effect on membrane fluidity is observed after treatment of cells resistant to nitrogen mustard. The biological consequence of a decrease in membrane fluidity was investigated by growing Friend erythroleukemia cells in the presence of 10 mM cholesterol hemisuccinate. This procedure raises the microviscosity of the plasma membrane and depresses cell proliferation.
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PMID:Inhibition of tumor growth by an alkylation of the plasma membrane. 610 May 83

The effects of modifications in the cholesterol and fatty acid contents of membranes on the transport of potassium have been studied in Mycoplasma mycoides subspecies capri. A decrease in the cholesterol content from 110 micrograms/mg of membrane protein to less than 10 micrograms/mg of membrane protein is associated with a decrease in the level of intracellular potassium from 40 micrograms of K/mg of protein to 23 micrograms of K/mg of cell protein. Replacement of oleate plus palmitate by elaidate alone in the growth medium has only limited effects on the intracellular K content. In metabolizing cells, 42K influxes were 0.42, 0.65, and 0.69 micrograms of K/mg of cell protein per min for cholesterol-rich cells supplemented with elaidate or with oleate plus palmitate and for cells adapted to low cholesterol and supplemented with elaidate, respectively. This increase in influx was associated with an increase in membrane fluidity as determined by fluorescence polarization experiments in which 1,6-diphenyl-1,3,5-hexatriene was used as a probe. For elaidate-supplemented cells, examination of the temperature dependence of 43K influx revealed the existence of a break or a discontinuity at temperatures corresponding to modifications in the physical state of the membrane. The lack of correspondence between the patterns of K+ influx and the Mg++-adenosine triphosphatase (ATPase) activity indicates that the sensitivity of this influx to the physical state of the membrane is not attributable to the Mg++-ATPase but likely reflects an effect of membrane lipids on the K+ carrier itself.
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PMID:Recent developments in the study of potassium transport in Mycoplasma mycoides subspecies capri. 612 24

Preincubation of rabbit thymocytes and lymph node cells for 20 h in 10% rabbit serum and subsequent exposure of these cells to concanavalin A resulted in a 70-100% increase in (Na+ + K+)-ATPase activity. The (Na+ + K+)-ATPase activity of rabbit lymph node cells and spleen lymphocytes was increased while that of erythrocytes did not show any response to concanavalin A exposure. Since only inhibition (50%) was observed when crude microsomes from rabbit thymocytes were incubated with concanavalin A, activation of (Na+ + K+)-ATPase appeared to require intact cells. Incubation of rabbit thymocytes in 10% rabbit serum for 20 h resulted in slightly increased fluidity of the innermost lipids of the cell membranes, as measured by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene. Fluidity changes did not appear to be the mechanism of activation of ATPase by concanavalin A, since incubation of cells with concanavalin A for 1 h had no effect on membrane fluidity in either freshly isolated or 20-h preincubated thymocytes. Compared with fresh thymocytes, preincubated cells had about twice the number of concanavalin A binding sites. Preincubated thymocytes became temporarily permeable to trypan blue after concanavalin A exposure. The percentage of cells taking up dye reached a maximum of 65% at 45-60 min, but decreased to 18% after a total of 3 h of incubation.
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PMID:Changes in (Na+ + K+)-ATPase activity associated with stimulation of thymocytes by concanavalin A. 613 5


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