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)

ATP stimulated the accumulation of 45Ca2+ by chromaffin granule ghosts which contained 5 mM oxalate to trap transported calcium within the lumen. Inasmuch as the ATP-dependent 45Ca2+ transport was resistant to 25 mM ammonium acetate as well as the proton ionophore, carbonylcyanide-m-chlorophenylhydrazone, the chromaffin granule proton translocating ATPase does not provide the energy for this process. Instead, we suggest that chromaffin granules contain a calcium translocating ATPase which catalyzes the 45Ca2+ uptake directly. The observation that chromaffin granules bind to a monoclonal antibody raised against a calcium pump from bovine brain supports this hypothesis.
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PMID:Biochemical and immunological evidence for a calcium pump in chromaffin granules. 297 54

Effects of 3,3',4',5-tetrachlorosalicylanilide (TCS), a lipophilic weak acid, on Ca2+ uptake and ATP hydrolysis by the sarcoplasmic reticulum calcium pump were characterized to obtain insight into the possible role of hydrophobic portions of the Ca2+-ATPase in the catalytic mechanism of the enzyme. TCS exhibited both the stimulatory and inhibitory effects on the calcium pump activities depending on its concentration. At optimal concentrations, it increased these activities by up to 5-fold at pH 7.0 and 6 degrees C. Analysis of partial reactions of ATP hydrolysis by the purified ATPase revealed that TCS accelerated Ca2+ release from the ADP-sensitive phosphoenzyme up to 6-fold, whereas it affected other reaction steps to a much less extent, indicating that the site of the stimulatory action of TCS is rather specific in terms of the reaction sequence. These effects of TCS became less prominent at higher temperatures, although the enzyme-TCS interactions as detected in the direct binding experiment or by measurement of quenching of protein fluorescence were not affected by a similar change in temperature. The TCS effects were also dependent on pH of the 8.0 suggested that the protonated form of TCS is responsible for both the stimulatory and inhibitory effects of the drug. These results, taken together with those obtained previously with a spin-labeled probe (Barratt, M. D., and Weaver, A. C. (1979) Biochim. Biophys. Acta 555, 337-348), may suggest that TCS stimulates the calcium pump activity through its effect on the lipid bilayer, although its direct action on hydrophobic portion(s) of the ATPase protein cannot be ruled out.
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PMID:Mechanism for 3,3',4',5-tetrachlorosalicylanilide-induced activation of sarcoplasmic reticulum ATPase. 297 65

Drug-induced taurine depletion of rat heart led to the accumulation of free CoA, free carnitine and long-chain acylcarnitine, but a small decrease in long-chain fatty acyl-CoA. Although elevations in total tissue long-chain acylcarnitine levels have been linked to defective membrane function and the association of long-chain acylcarnitines with extramitochondrial membranes, these effects were absent in isolated sarcoplasmic reticulum prepared from taurine-depleted hearts. In contrast to the sarcoplasmic reticulum data, taurine depletion was associated with a significant decrease in ATP-dependent calcium uptake by isolated sarcolemmal vesicles. The major effect of taurine depletion on the sarcolemma was a 2-fold decrease in both the Vmax of calcium transport and the activity of the Ca2+ -stimulated ATPase. Sarcolemmal vesicles prepared from taurine-depleted hearts also exhibited a decreased capacity to transport calcium in exchange for sodium, although the initial rate of the process was unaffected by taurine depletion. Since incubation of sarcolemma from taurine-depleted hearts with taurine could not overcome the effects of taurine depletion, it was concluded that the effects of taurine were not caused by a direct interaction of it with the calcium pump. Possible mechanisms of taurine action are discussed.
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PMID:Regulation of calcium transport in drug-induced taurine-depleted hearts. 297 16

Increased radiocalcium influx, decreased Ca-ATPase activity and cAMP concentration were observed in Ehrlich carcinoma cells submitted to hyperthermia temperature (45 degrees C). The significant augmentation of mitochondrial calcium that is simultaneous to an inhibition of the calcium pump appears to indicate a heat-induced failure of the system of calcium-extrusion that may be responsible for cell inactivation and death through cell toxic death by calcium overloading. The decreased cAMP concentration appears to corroborate the influx of calcium.
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PMID:Calcium, calcium-ATPase and cyclic AMP changes in Ehrlich ascites cells submitted to hyperthermia. 299 11

Ontogenetic changes in calcium transport mediated by the sarcolemmal Na-Ca exchanger and by the sarcoplasmic reticulum calcium pump were studied in crude membranes from chick heart. Transport activities were evaluated per mass of membrane protein and heart tissue. Relative to unit heart mass Na-Ca exchange activity increases linearly from embryonic day 4 to day 10 of newborn stage. The overall increase is about 20-fold. An excellent correlation exists between activity of sodium gradient-induced calcium uptake and ouabain-sensitive (Na,K)-ATPase in crude membranes of embryonic, newborn and adult hearts. In the same membrane preparations active calcium uptake into vesicles of sarcoplasmic reticulum increases about 3-fold from embryonic day 4 to embryonic day 7, and then increases continuously until day 20. This is followed by a 3-fold elevation in reticular calcium accumulation at hatching on day 21. Maximal sarcoplasmic reticulum calcium transport activity reached at day 10 after hatching is 40- to 50-fold greater than activity values at embryonic day 4. In adult hearts the activities of both Na-Ca exchange and reticular calcium uptake drop to levels characteristic for the late embryonic period. This comparative study of sarcolemmal sodium gradient-dependent calcium flux and reticular calcium sequestration demonstrates that during chick heart differentiation the two calcium transport systems do not develop in parallel. Na-Ca exchange appears to play a greater role in calcium control of embryonic as compared to newborn and adult hearts. By contrast, the contribution of sarcoplasmic reticulum calcium transport to cardiac calcium movements becomes more predominant during and after hatching.
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PMID:Sarcolemmal Na-Ca exchange and sarcoplasmic reticulum calcium uptake in developing chick heart. 302 91

In previous studies from this laboratory, it was noted that opioids in vitro reduced human red blood cell deformability. The effect was found to be dose-dependent, naloxone reversible and preferentially selective kappa ligands exhibited the highest potency. To extend these findings studies were carried out using rat erythrocytes. The time required for erythrocytes to pass through a 5.0 um pore membrane was determined and used as an index of deformability. Opioids added in vitro produced inhibition of deformability in a dose-dependent, naloxone reversible manner. Injecting naive animals with morphine or nalbuphine also produced dose related reductions in red cell deformability. The degree of inhibition produced by nalbuphine correlated well with its plasma concentrations as measured by high performance liquid chromatography (HPLC). Chronic morphine treatment by pellet implantation resulted in the development of tolerance as evidenced by a loss in the ability of morphine in vitro to inhibit red cell deformability. Addition of naloxone resulted in a decrease in filtration time. Thus, the data confirm and extend previous findings on human red blood cells. In as much as previous data from this laboratory demonstrated that opioids inhibit calcium flux from erythrocytes by inhibiting calcium-ATPase and calcium efflux is necessary for normal deformability, it is concluded that opioids act to reduce red cell deformability by inhibition of the calcium pump.
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PMID:Opioids and rat erythrocyte deformability. 312 33

The coupling of calcium transport to ATP hydrolysis in rabbit muscle sarcoplasmic reticulum vesicles was determined under steady-state conditions in the presence of 5 mM oxalate and using various concentrations of vesicles to modulate the concentration of free Ca2+ in the medium. This experimental approach takes advantage of the fact that at high concentrations of vesicles the slow rate of liberation of Ca2+ from its oxalate complex becomes rate limiting for pumping, therefore pushing the steady-state levels of this cation to very low values. A reduction in the number of calcium ions transported per ATP cleaved from a value near 2 at a low concentration of vesicles (high medium Ca2+ concentration) to a limiting value of about 1 at a very high concentration of vesicles (low medium Ca2+ concentration) was observed. A marked decrease in the specific ATPase activity was also found to take place as the concentration of the sarcoplasmic reticulum vesicles was increased to high levels and the concentration of medium Ca2+ declined. The data presented indicate that binding of 1 Ca2+ to the sarcoplasmic reticulum ATPase is sufficient to activate the pump. Furthermore, these findings support the existence of a control mechanism for the calcium pump that helps to avoid a futile cycle of ATP cleavage with no net transport of calcium and that increases the pumping capability at low concentrations of free Ca2+.
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PMID:Modulation of stoichiometry of the sarcoplasmic reticulum calcium pump may enhance thermodynamic efficiency. 315 60

The heart and gill of a freshwater fish Saccobranchus fossilis have been shown to contain a Ca2+-activated ATPase involved in Ca2+ transport. Enzyme showed optimal activity at 3 mM Ca2+ and 3 mM ATP for gills and at 3 mM Ca2+ and 1 mM ATP for heart. Mg2+ was equally effective in stimulating enzyme activity but was not essential for hydrolysis. Maximum activity was found in heart ventricular muscles as compared to gills. Among all the metals tested Hg2+ was the most toxic (IC50, 0.75 and 0.85 microM for heart and gill, respectively) followed by Pb2+, Mn2+, and Cd2+. The inhibition was concentration dependent and reached almost 100% with each metal at the highest concentration. Stimulation of enzyme activity was observed at lower concentrations of Mn2+ and Cd2+ but not with Pb2+ and Hg2+. Stimulation was more pronounced with Mn2+ than with Cd2+ in both heart and gills. The results indicated that the inhibitory effect of these metals might be through the Ca2+-ATPase which is a manifestation of the calcium pump in various tissues.
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PMID:The effects of some divalent metals on cardiac and branchial Ca2+-ATPase in a freshwater fish Saccobranchus fossilis. 315 61

It has been suggested that the parathyroid glands and the kidneys are insensitive to the high extracellular calcium levels found in familial benign hypercalcaemia (FBH) (familial hypocalciuric hypercalcaemia) and that there may be a general disorder of the plasma membrane 'calcium pump'. We have found that the activity of the calcium-stimulated, magnesium-dependent ATPase of erythrocyte ghost membranes from patients with FBH was significantly higher (p less than 0.01) than that from normal subjects. Values in FBH, as a group, were higher than those in primary hyperparathyroidism, but the difference was not significant. We suggest that the membrane abnormality in FBH could be a disorder of the regulation of the calcium pump.
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PMID:Calcium-ATPase activity in erythrocyte ghosts from patients with familial benign hypercalcaemia. 316 Jan 2

Proteolytic digestion and indirect immunostaining were used to compare the platelet and sarcoplasmic reticulum Ca2+-ATPase proteins. When the platelet and sarcoplasmic reticulum Ca2+-ATPase proteins were digested in the native state with trypsin, the platelet Ca2+-ATPase, which had an apparent undigested molecular mass of 103 kDa, yielded 78-kDa and 25-kDa fragments. Calcium transport activity depended on the integrity of the 103-kDa protein, while the digested protein had residual ATPase activity. Tryptic digestion of the sarcoplasmic reticulum pump protein, which also had an undigested molecular mass of 103 kDa, yielded products with apparent molecular masses of 55 kDa, 36 kDa, and 26 kDa. Distinct patterns were also observed when the platelet and sarcoplasmic reticulum calcium pump proteins were digested with chymotrypsin and Staphylococcus aureus protease in the presence of sodium dodecyl sulfate. Chymotrypsin digestion of the platelet protein resulted in the appearance of products with apparent molecular masses of 70 kDa, 39 kDa, and 31 kDa, while a similar digestion of the sarcoplasmic reticulum calcium pump protein yielded 54-kDa, 52.5-kDa, 46-kDa, 41-kDa, and 36-kDa fragments. Exposure of the sarcoplasmic reticulum and platelet Ca2+-ATPase proteins to S. aureus protease also yielded dissimilar fragmentation patterns. These results indicate that the Ca2+-ATPases from platelets and sarcoplasmic reticulum are distinct proteins.
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PMID:Evidence that platelet and skeletal sarcoplasmic reticulum Ca2+-ATPase are structurally distinct. 316 Jun 95


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