Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nippostrongylus brasiliensis infection of the rat resulted, at day 10 of infection, in decreased levels of jejunal enterocyte sodium-potassium-activated adenosine triphosphatase (Na,K-ATPase) and potassium-activated p-nitrophenyl phosphatase (K-pNPPase) activities. Parallel decreases occurred in active sodium efflux from jejunal enterocytes in the presence and absence of actively transported monosaccharides. Ileal enterocyte Na,K-ATPase and K-pNPPase activities were significantly increased, as was active sodium efflux. In contrast to controls, the presence of monosaccharides produced a stimulation of active sodium efflux from ileal enterocytes derived from infected rats. Enzyme and sodium transport changes in the jejunal enterocytes probably reflect cellular immaturity. Functional changes in ileal enterocytes probably represent a compensatory phenomenon.
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PMID:Changes in Na,K-ATPase, sodium ion, and glucose transport in isolated enterocytes in an experimental model of malabsorption. 255 21

Increased levels of a humoral inhibitor of active sodium transport have been associated with the response to acute and chronic hypervolemia and various forms of experimental as well as human essential hypertension. In this report, we describe the purification of inhibitors of Na+, K+-adenosine triphosphatase (ATPase) from the plasma of volume-expanded individuals. Of the two amphipathic materials obtained, only one of the factors when present in high concentrations showed the slow time-dependent component of inactivation similar to that of the cardiac glycosides. Inhibition was reduced in the presence of plasma proteins and was freely reversible. Both factors inhibited potassium-dependent p-nitrophenylphosphatase activity and specific [3H]ouabain binding in a manner similar to the cardiac glycosides. In contrast to ouabain and vanadate, however, high concentrations of potassium or norepinephrine, respectively, did not affect the magnitude or kinetic characteristics of inhibition. Structural analysis by mass spectroscopy showed a mass of 444 for factor 1, whereas factor 2 was conclusively identified as lysophosphatidylcholine-gamma-palmitoyl. These factors probably inhibit Na+, K+-ATPase by a nonspecific mechanism involving reversible perturbation of lipid-enzyme interactions required for normal catalytic activity. The significance of these factors as modulators of sodium transport may be limited to pathological states associated with abnormalities in plasma protein binding or lipid metabolism. They do not appear to be directly related to the humorally mediated disturbance of cellular sodium transport in hypertension.
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PMID:Purification and characterization of digitalislike factors from human plasma. 282 70

A 6.5-kilobase fragment of genomic DNA from mutant mouse cells under ouabain selection pressure conferred ouabain resistance when transfected into ouabain-sensitive CV1 green monkey fibroblasts. Ouabain resistance was induced in the presence of 10 microM ouabain. Amiloride (500 microM) completely blocked ouabain-insensitive 86Rb+ uptake into these cells. Plasma membranes from these cells demonstrated little sodium-dependent adenosine triphosphatase (ATPase) activity but had potassium-dependent and ouabain-resistant p-nitrophenylphosphatase activity. Like Na+,K+-ATPase this activity was vanadate- and sodium-inhibitable. Also, like the Na+,K+-ATPase, sodium inhibition of the p-nitrophenylphosphatase was reversed by 10 microM adenosine 5'-triphosphate.
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PMID:Membrane biochemistry of the ouabain-resistant potassium transport system. 282 73

Sensitivity to ethanol, temperature dependence of apparent K+ affinity and temperature dependence of enzyme conformation of K+-p-nitrophenylphosphatase activity associated with (Na+,K+)-adenosine triphosphatase in brain membranes from rats treated chronically with liquid diets containing ethanol or isocaloric amounts of carbohydrate were compared. Three weeks' diet resulted in behavioral tolerance to ethanol. K+-p-nitrophenylphosphatase activity from tolerant rats was less sensitive than that from controls to inhibition by added ethanol, especially under conditions most favorable to ethanol inhibition. Apparent affinity for K+ was greater at all temperatures in ethanol-treated rats, and apparent delta S and delta H for K+-activation were reduced, opposite to effects of ethanol added in vitro. The amount of enzyme in the K+-sensitive conformation was greater at all temperatures in ethanol-treated rats, again opposite to effects of added ethanol. Apparent delta S and delta H of the conformational transition from E1 to E2 were reduced by ethanol treatment. These results are consistent with an apparent adaptation to chronic ethanol exposure in which membrane fluidity, at least in the neighborhood of (Na+,K+)-adenosine triphosphatase sites, is reduced, resulting in greater K+ affinity, more favorable transition to the phosphatase form of enzyme, a smaller entropy difference between native and K+-activated enzyme and reduced sensitivity to ethanol.
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PMID:Chronic ethanol and (Na+-K+)-adenosine triphosphate: apparent adaptation in cation binding and enzyme conformation. 298 12

Hydrolysis of adenosine 5'-triphosphate (ATP) and p-nitrophenyl phosphate by the hydrogen ion-transporting potassium-stimulated adenosine triphosphatase (H,K-ATPase) was investigated. Hydrolysis of ATP was studied at pH 7.4 in vesicles treated with the ionophore nigericin. The kinetic analysis showed negative cooperativity with one high affinity (Km1 = 3 microM) and one low affinity (Km2 = 208 microM) site for ATP. The rate of hydrolysis decreased at 2000 microM ATP indicating a third site for ATP. When the pH was decreased to 6.5 the experimental results followed Michaelis-Menten enzyme kinetics with one low affinity site (Km = 116 microM). Higher concentrations than 750 microM ATP were inhibitory. Proton transport was measured as accumulation of acridine orange in vesicles equilibrated with 150 mM KCl. The transport at various concentrations of ATP in the pH interval from 6.0 to 8.0 correlated well with the Hill equation with a Hill coefficient between 1.5-1.9. The concentration of ATP resulting in half-maximal transport rate (S0.5) increased from 5 microM at pH 6.0 to 420 microM at pH 8.0. At acidic pH the rate of proton transport decreased at 1000 microM ATP. The K+-stimulated p-nitrophenylphosphatase (pNPPase) activity resulted in a Hill coefficient close to 2 indicating cooperative binding of substrate. The pNPPase was noncompetitively inhibited by ATP and ADP; half-maximal inhibition was obtained at 2 and 100 microM, respectively. Phospholipase C-treated vesicles lost 80% of the pNPPase activity, but the Hill coefficient did not change. These kinetic results are used for a further development of the reaction scheme of the H,K-ATPase.
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PMID:Kinetics of the acid pump in the stomach. Proton transport and hydrolysis of ATP and p-nitrophenyl phosphate by the gastric H,K-ATPase. 298 93

Membrane-bound (H+ + K+)-ATPase purified from hog gastric mucosa was exposed to limited papain digestion. Such treatment resulted in a rapid inhibition of the K+-stimulated adenosine triphosphatase and p-nitrophenyl phosphatase activities, with about 90% of these activities lost after 3 min incubation at 37 degrees C with 0.1 units of papain per mg of enzyme protein. Parallel to the inhibition of the enzyme activities, there was a production of a 77 kDa membrane-bound fragment containing the aspartyl phosphate residue of the phospho-intermediate. This fragment accounted for about 45% of the total enzyme protein after the 3 min papain treatment. The digestion barely affected the steady-state level of phosphorylation, allowed the aspartyl phosphate of the 77 kDa fragment to undergo the transition to the E2P form, and did not significantly alter the fraction of ADP-sensitive phosphoenzyme. The presence of KCl, however, depressed the steady-state level of phosphoenzyme formed from [gamma-32P]ATP considerably less than that of the control enzyme. With further exposure to papain the 77 kDa peptide became fragmented into a 28 kDa soluble peptide that retained the phosphorylating site. Binding of fluorescein 5'-isothiocyanate (FITC) to the native enzyme did not affect the sites of papain hydrolysis because the same peptide fragments were obtained. The FITC reaction site was also in the 28 kDa soluble peptide fragment.
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PMID:Papain fragmentation of the gastric (H+ + K+)-ATPase. 303 Apr 30

We have developed a new cytochemical method for detecting the ouabain-sensitive, potassium-dependent p-nitrophenylphosphatase (K-NPPase) activity of the sodium-potassium-activated adenosine triphosphatase (Na-K ATPase) complex. The incubation medium contains p-nitrophenylphosphate (p-NPP) as substrate, cerium chloride as capture agent, Tricine buffer, MgCl2, and KCl. Tricine buffer protected against the medium turbidity caused by non-enzymatic reaction at pH 7.5. Biochemically, the accumulation of p-nitrophenol and phosphate in the reaction precipitate was proportionally related to the enzyme concentration. Ultracytochemically, the reaction products of the K-NPPase activity were localized as fine and uniform electron-dense deposits in the cytoplasmic side of specialized basolateral plasma membranes of cells of kidney distal convoluted tubules, secretory cells of salt gland, and marginal cells of stria vascularis. This method has the advantage of being useful at physiological pH.
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PMID:Cerium-based cytochemical method for detection of ouabain-sensitive, potassium-dependent p-nitrophenylphosphatase activity at physiological pH. 303 Nov 56

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

The effects of dimethyl sulphoxide and glycerol on ox brain microsomal Na(+)+K(+)-stimulated adenosine triphosphatase (EC 3.6.1.3), K(+)-stimulated p-nitrophenyl phosphatase and K(+)-dependent muscle pyruvate kinase (EC 2.7.1.40) were studied. Dimethyl sulphoxide at concentrations below 20% (v/v) was found to stimulate the p-nitrophenyl phosphatase and pyruvate kinase by increasing their affinity for K(+) but to inhibit the Na(+)+K(+)-stimulated adenosine triphosphatase. The latter enzyme activity was also inhibited by glycerol, which like dimethyl sulphoxide, stimulated the K(+)-activated p-nitrophenyl phosphatase at a wide range of concentrations. The solvent effects were promptly reversed by dilution. Similarity was found between glycerol and dimethyl sulphoxide, on one hand, and ATP, on the other, in their stimulatory effect and their ability to increase the ouabain- and oligomycin-sensitivity of the K(+)-stimulated p-nitrophenyl phosphatase. However, only the solvents, not the ATP, increased the binding of K(+) by the microsomes. From the above findings it is suggested that solvents may act on K(+)-dependent enzymes by altering the state of solvation of the activating cation as well as by changing the enzyme structure.
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PMID:Interaction of solvents with membranal and soluble potassium ion-dependent enzymes. 424 83

This study examined the effects of diet and treatment with noradrenergic receptor antagonists on weight gain and indices of Na+-K+-adenosine triphosphatase (ATPase) activity in the rat. When rats were fed a palatable cafeteria diet, their caloric consumption increased by about 80%, but they did not gain weight significantly. Ouabain binding and K+-p-nitrophenylphosphatase (NPPase) activity were increased in brown adipose tissue and soleus. These indices remained elevated after the rats were returned to a regular diet. When rats were fasted for 3 days, they lost weight, and the indices of Na+-K+-ATPase activity were markedly reduced in brown adipose tissue and soleus. After refeeding the fasted rats gained weight three times more rapidly than nonfasted rats with similar food intake. Indices of Na+-K+-ATPase activity remained as low as they had been when the rats were fasting. There was a consistent negative correlation between weight gain per calorie eaten and brown adipose tissue NPPase activity. Changes in Na+-K+-ATPase could therefore be involved in the effects of overfeeding and fasting on metabolic efficiency. Desmethylimipramine binding was increased by cafeteria diet and decreased by fasting, consistent with changes in sympathetic nervous system activity. Treatment with prazosin, an alpha 1-noradrenergic receptor antagonist, reduced Na+-K+-ATPase in either control or cafeteria diet-fed rats but did not alter the effect of cafeteria diet feeding. By contrast, treatment with propranolol, a beta-receptor antagonist, prevented the increase in Na+-K+-ATPase during cafeteria diet feeding.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Caloric intake and Na+-K+-ATPase: differential regulation by alpha 1- and beta-noradrenergic receptors. 608 94


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