Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The stimulation by calcium and magnesium of ATPase activity of isolated ghosts, of water-soluble protein (spectrin), and of residual vesicles, derived from normal erythrocytes and from hereditary spherocytes (H.S.), has been measured. The ATPase activity found in normal water-soluble protein (WSP) at low levels of calcium (0.1-2.0 mM) is essentially absent in H.S. water-soluble protein, but the ATPase activity with magnesium and with high levels of calcium (60-100 mM) is the same in H.S. and normal WSP. Compared to normal, H.S. ghosts have increased Mg2+-stimulated activity. This increased activity is retained by the sedimentable vesicles ("residue") after extraction of the ghosts with 0.025 mM EDTA. The Ca2+, Mg2+-ATPase associated with the calcium pump is not significantly different in H.S.
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PMID:Absence of one component of spectrin adenosine triphosphatase in hereditary spherocytosis. 12 93

Calmodulin-free ghost membranes were prepared from erythrocytes of kwashiorkor children and from healthy children in the same age bracket. In the absence of calmodulin, the specific activity of Mg2+-dependent Ca2+-pumping ATPase (Ca2+ + Mg2+-ATPase) of kwashiorkor membranes was more than 40 percent lower than the specific activity of the normal enzymes, whose maximum velocity was increased by at least four-fold by the modulator protein. In contrast, the maximum velocity of the enzymes of kwashiorkor membranes was enhanced by calmodulin by about 1 1/2 times the basal activity of the normal enzymes and by 2 times the basal activity of the kwashiorkor enzymes. The affinity of the pump for ATP was lower in the membranes of kwashiorkor children (Km for ATP = 30.6 +/- 2.8 microM ATP) in comparison to normal membranes (Km for ATP = 21.7 +/- 2.0 microM ATP). Similarly, calmodulin-affinity of the enzymes, was lower in kwashiorkor membranes than in the normal membranes irrespective of source of calmodulin. Calmodulin from haemolysates of kwashiorkor red cells activated the enzymes of normal and kwashiorkor membranes to the same degree as calmodulin partially purified from the haemolysate of healthy children. A determination of the dependence of the activity of the pump on calcium in the absence and presence of calmodulin reveals that the affinity of the kwashiorkor enzymes for Ca2+ is at least 70 percent lower than that of enzymes of normal membranes. Altogether, these findings suggest that the Ca2+-pumping ATPase of kwashiorkor membranes is less functional than the enzymes of healthy erythrocytes.
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PMID:Erythrocyte membrane (Ca2+ + Mg2+)-ATPase in human protein-energy malnutrition. 255 Jan

Treatment with calcitriol of isolated cartilage cells derived from epiphyseal growth plates of rachitic chicks results in reduced intracellular calcium concentrations. The reduction in calcium was found to correlate with increased activity of Ca2+-ATPase. The activities of Na+-K+-ATPase and of Mg2+-ATPase did not change in response to the treatment with calcitriol. It is suggested that calcitriol regulates intracellular calcium by modulating the activity of the Ca2+-pumping ATPase.
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PMID:Calcitriol increases Ca2+-ATPase activity. 303 61

The Ca2+-pumping ATPase from human erythrocyte membranes, purified nearly to homogeneity (Niggli, V., Penniston, J. T., and Carafoli, E. (1979) J. Biol. Chem. 254, 9955-9958), can be reconstituted into phospholipid vesicles. The purified and the reconstituted forms of the enzyme displayed the properties expected of the intact Ca2+ pump; they had an appropriate (Ca2+-Mg2+)-ATPase activity which displayed a relatively low affinity for Ca2+. Added calmodulin increased both the maximum rate and the affinity for Ca2+ of the enzyme. Mg2+ alone caused no significant ATP hydrolysis in the purified enzyme, indicating that the Mg2+-ATPase is a separate enzyme. Vesicles of the reconstituted enzyme accumulated Ca2+ with a ratio of Ca2+ accumulated to ATP hydrolyzed of approximately 1. Ca2+ accumulation and ATPase of the reconstituted enzyme were inhibited concurrently by vanadate ion, with a K 1/2 for inhibition which was indistinguishable from that observed for the (Ca2+-Mg2+)-ATPase in whole erythrocyte ghosts. While the above properties were all consistent with those observed for the (Ca2+-Mg2+)-ATPase in whole erythrocyte ghosts, the purified enzyme displayed an unexpected response to acidic phospholipids. Enzyme reconstituted with or prepared in phosphatidylserine acted as if calmodulin were already present, and added calmodulin caused no effect beyond that due to phosphatidylserine. This mimicry of the calmodulin effect by acidic phospholipids is similar to that reported for cyclic nucleotide phosphodiesterase (Wolff, D. J., and Brostrom, C. O. (1976) Arch. Biochem. Biophys., 173, 720-723).
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PMID:Purified (Ca2+-Mg2+)-ATPase of the erythrocyte membrane. Reconstitution and effect of calmodulin and phospholipids. 610 53

There is growing evidence for essential or genetic hypertension to be associated with certain membrane abnormalities. We have published previous results on biochemical studies performed on erythrocyte membranes of the Okamoto-Aoki spontaneously hypertensive rat (SHR) and its normotensive control the WKY, reporting evidence of structural and functional alterations in the membranes. These changes could lead to increased calcium permeability and possibly compensatory increase in calcium pump activity that we observed concurrently. Chronic ethanol consumption resulted in mild hypertension in the rats used in the present study. The elevation in blood pressure is not associated with gross membrane changes in the erythrocyte. We noticed, however, that there is a slight elevation in the high affinity Ca2+/Mg2+-ATPase activities together with a trend towards higher osmotic fragility in the red cells of the ethanol-treated rats when compared with controls. These changes could be the result of concurrent reduction in plasma and membrane cholesterol contents also observed in the ethanol-treated animals.
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PMID:Erythrocyte membrane properties of the chronic alcoholic rat. 614 Jan 54

Biochemical studies were carried out to demonstrate for the first time direct evidence for the presence of ATP-dependent calcium uptake activity in plasma membrane isolated from the head of bull spermatozoa. The purified plasma membrane vesicles contain also Na+-K+-ATPase, Mg2+-ATPase and Ca2+-ATPase activities. All the activities mentioned were followed in parallel in isolated plasma membranes from the sperm tail. These results together with others, suggest the involvement of the ATP-dependent calcium pump in regulation of intracellular calcium in the process of capacitation and acrosome reaction.
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PMID:Evidence for the presence of ATP-dependent calcium pump and ATPase activities in bull sperm head membranes. 614 36

The ability of N-acylethanolamines (pharmacologically active lipid metabolites which accumulate in canine myocardium during experimentally induced infarctions) to alter Ca2+ fluxes in a biological membrane system was studied using sarcoplasmic reticulum vesicles prepared from rabbit skeletal muscle. The effects of two N-acylethanolamines, the N-oleyl and N-lauryl derivatives, were compared to those of the lipophilic drugs, dibucaine and propranolol. The rate and extent of Ca2+ sequestration, Ca2+-Mg2+-ATPase activity and retention time of Ca2+ by the vesicles were all stimulated at low concentrations of the four compounds studied and inhibited at higher concentrations. The stoichiometry between Ca2+-pumping rates and ATPase activity was partially "uncoupled" indicating that both the calcium pump and the membrane permeability were affected by the drugs. However, although all four compounds exhibited the same qualitative behavior, the effects of the two N-acylethanolamines were more pronounced than dibucaine and propranolol and occurred at much lower concentrations. These results suggest that the N-acylethanolamines may have important physiological effects in the myocardium and, at least at lower concentrations, stimulate myocardial contractility by increasing the rate of calcium flux across the sarcoplasmic reticulum.
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PMID:The alteration of rabbit skeletal sarcoplasmic reticulum function by N-acylethanolamine, a lipid associated with myocardial infarction. 621 43

Experiments with highly purified preparations of Ca2+,Mg2+-ATPase solubilized from sarcolemma and a fraction of inside-out sarcolemmal vesicles were performed to study the kinetics of inhibitory effects of eosin Y (0-100 microM) on the catalytic and transport activity of Mg2+,ATP-dependent calcium pump of myometrial cell plasma membrane. For both the Ca2+,Mg2+-dependent ATP hydrolysis and the Mg2+, ATP-dependent accumulation of Ca2+ the apparent inhibitory constant Ki was 0.8 microM. However, eosin Y used at concentrations of up to 100 microM had absolutely no effect on Na+-Ca2+ exchange in the plasma membrane fraction. This inhibitor decreased the turnover rate of purified Ca2+,Mg2+-ATPase determined both by Mg2+ and ATP. However, the affinity of purified Ca2+,Mg2+-ATPase for Mg2+ increased, and its affinity for ATP decreased in the presence of eosin Y. In the case of Mg2+,ATP-dependent Ca2+ transport, eosin Y decreased the turnover rate of the calcium pump whose affinity for Mg2+ and ATP displayed virtually no dependence on the presence of the inhibitor in the incubation medium. The possibility of the use of eosin Y in model experiments for identification of Mg2+, ATP-dependent and Na+-dependent calcium fluxes from smooth muscle cells into the intercellular milieu is discussed.
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PMID:Effects of eosin Y on the catalytic and functional activities of Mg2+,ATP-dependent calcium pump of smooth muscle cell plasma membrane. 966 8