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)

1. The coupling ATPase of Paracoccus denitrificans can be removed from the membrane by washing coupled membrane fragments at low salt concentrations. 2. This ATPase resembles coupling ATPases of mitochondria, chloroplasts and other bacteria. It is a negatively charged protein of molecular weight about 300,000. An inhibitor protein in bound tightly to the ATPase in vivo, and can be destroyed by trypsin treatment. 3. ATP and ADP are found tightly bound to the coupling ATPase of P. denitrificans, both in its membrane-bound and isolated state. The ATP/ADP ratio on the enzyme is greater than one. 4. Under de-energised condtions, the bound nucleotides are not available to the suspending medium. When the membrane is energised however, the bound nucleotides can exchange with added nucleotides and incorporate 32Pi. 32Ppi is incorporated into the beta and gamma positions of the bound nucleotides, but beta-labelling probably does not occur on the coupling ATPase. 5. Uncouplers inhibit the exchange of the free nucleotides or 32Pi into the bound nucleotides, while venturicidin (an energy transfer inhibitor) and aurovertin stimulate the exchange. 6. The response of the bound nucleotides to energisation is consistent with their being involved directly in the mechanism of oxidative phosphorylation.
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PMID:Tightly bound nucleotides of the energy-transducing ATPase, and their role in oxidative phosphorylation. I. The Paracoccus denitrificans system. 13 62

Ouabain circulating in blood inhibits Na-K-ATPase in the gills of seawater eels at a concentration similar to that necessary for inhibition in vitro. By contrast, a much higher concentration is required when ouabain is applied to the exterior of the gill. Inhibition by external ouabain occurs only when the drug gains access to the circulation of the fish, as evidenced by simultaneous inhibition of Na-K-ATPase in the kidney. These results suggest that the Na-K-ATPase of gill chloride cells faces inward, lining intracytoplasmic tubular channels continuous with the extracellular fluid. Inhibition of gill Na-K-ATPase by ouabain in intact salt water eels results in almost complete inhibition of the efflux of both Na+ and Cl-. The efflux is tritiated water was much less reduced, to 60% of normal. Since chloride is actively transported outward across the gill of seawater teleosts, it is suggested that active chloride transport is coupled to Na-K-ATPase. A neutral sodium chloride carrier is postulated that is energized by the movement of sodium from extracellular fluid down its electrochemical gradient into the chloride cell.
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PMID:Ouabain inhibition of gill Na-K-ATPase: relationship to active chloride transport. 13 54

Filamin, a major high-molecular-weight protein of chicken gizzard smooth muscle, was purified to homogeneity by salt extraction, ammonium sulfate precipitation, agarose gel filtration, and diethylaminoethylcellulose ion-exchange chromatography. Purified filamin is an asymmetric oligomer consisting of two large subunits of identical size (2 X 250 000 daltons) as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, chemical cross-linking, sedimentation analysis (s10, wo = 10S) and Stokes'radius estimation (a = 120 A), It has no intersubunit disulfide but appears from oxidation studies to have adjacent thiols near the subunit interface. Filamin contains no amino sugars, methylated lysine, methylated histidine, or hydroxyproline, nor does it exhibit myosin-like ATPase activities. Its amino acid composition and physical properties differ from those of gizzard myosin, for which a pruification procedure is described. Filamin and the protein spectrin of erythrocyte membranes have strikingly similar physical properties, but they are chemically distinct.
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PMID:Filamin, a new high-molecular-weight protein found in smooth muscle and nonmuscle cells. Purification and properties of chicken gizzard filamin. 13 17

In the present investigation the results of a lead salt technique and two calcium salt techniques for the deomonstration of the activity of myosin adenosine triphosphatase in sections of both normal and pathological human skeletal muscle specimens are compared. It was seen that the histochemical results obtained by the different techniques are similar, especially with regard to the identification of fibre-types. It can be clearly stated, that the alkaline phosphatase activity present in muscle fibers of diseased skeletal msucles revealed only a very slight activity with the substrate ATP, so the alkaline phosphatase activity in general did not disturb the reliability of the different myosin ATPase techniques. Moreover it was found that the presence of the mitochondrial Ca2+ -ion activated ATPase with a high pH-optimum in muscle fibers did not give rise to faulty results. From studies with dinitrophenol it can be concluded that this substance activates the myosin ATPase present in type I fibres especially.
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PMID:The value of enzyme histochemical techniques in the classification of fibre types of human skeletal muscle. 2. The histochemical demonstration of myosin adenosine triphosphatase in skeletal muscles from adult patients with or with no diseases of the neuromuscular system. A comparison between results obtained by calcium salt and lead salt techniques. 14 Aug 52

Myosin from the hearts of thyrotoxic animals (myosin-T) exhibits elevated Ca2+-ATPase activity. To clarify the physiological significance of this increased activity, we have investigated the steady state kinetics of the interaction of actin and MgATP with the double-headed heavy meromyosin subfragment of cardiac myosin from thyrotoxic rabbits (HMM-T). The enhanced Ca2+-ATPase activity of myosin-T was completely retained in HMM-T. The Vmax for actin-activated MgATP hydrolysis by HMM-T (1.08 +/- 0.10 mumol of Pi/mg/min). Under physiological ionic conditions, the Vmax was 0.14 +/- 0.02 mumol of Pi/mg/min as compared with the normal value of 0.08 +/- 0.01 mumol of Pi/mg/min. Furthermore, the salt dependence of Vmax and Kapp for the actin-activated ATPase of HMM-T differed markedly from normal and resembled that usually associated with the single-headed (S1) cleavage product of myosin. These results suggest that the changes in enzymatic properties of myosin-T are responsible for the increased speed of contraction observed in the hearts of thyrotoxic animals. Also, the alteration in the interaction of HMM-T with actin suggests that a loss of cooperativity between the myosin heads may occur.
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PMID:Enzymatic properties of the heavy meromyosin subfragment of cardiac myosin from normal and thyrotoxic rabbits. 14 72

Cholestatic jaundice is one complication of nonhepatic gram-negative bacterial infection. The endotoxin of Escherichia coli has been reported to cause cholestasis by inhibiting the bile salt-independent fraction (BSIF) of bile in the perfused rat liver. Accordingly, the effects of lipopolysaccharides (LPS) of E. coli and Salmonella enteritidis on the Na+, K+-adenosinetriphosphatase (ATPase) in canalicular-enriched plasma membranes of rate liver were examined. At 20 microgram/ml, both endotoxins inhibited this enzyme by approximately 40%. Maximal inhibition (70%-80%) occurred at concentrations of greater than or equal to 120 microgram/ml. The LPS of neither organism exerted any effect on the activity of Mg++-ATPase or 5'-nucleotidase in the same preparations. Inhibition by the E. coli LPS appeared to be noncompetitive in nature, and the calculated Ki was 45 microgram/ml. Since the Na+, K+-ATPase may be responsible for the elaboration of BSIF, inhibition of this enzyme could be the underlying mechanism for the endotoxin-induced cholestasis.
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PMID:Inhibition of Na+, K+-adenosinetriphosphatase by endotoxin: a possible mechanism for endotoxin-induced cholestasis. 14 99

The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 muM ouabain (containing 5 muCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia.
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PMID:Basolateral plasma membrane localiztion of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland. 14 41

Erythrocytes and their isolated membranes display ATP-dependent endocytosis. To localize the enzymes responsible for this phenomenon, the erythrocyte membranes (ghosts) were fractionated under conditions which retained ATPase activity. Fractionation of the ghosts resulted in three fractions: spectrin-actin, the peripheral proteins soluble in high salt, and the smooth membrane containing integral proteins. On the average, 87% of the protein and 88% of the phosphorus of the original ghosts were recovered in these fractions, and all of the kinds of ATP-splitting activities of the membrane were recovered in the smooth membrane. A tiny ATPase activity, detectable by special methodology in spectrinactin, could have been due to contamination with membranous material. Although the purified spectrin-actin did not have a significant ATPase of its own, it stimulated the Ca2+, Mg2+-ATPase of the smooth membrane significantly, suggesting a cooperative interaction between these two fractions. This segregation of the ATPase activities into the smooth membrane, combined with the energy dependence of endocytosis, showed that the smooth membrane must be involved in the energy production for endocytosis. The possibility that the spectrin-actin filaments cooperate with a myosinlike ATPase in the membrane to generate membrane movements is discussed.
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PMID:Peripheral proteins and smooth membrane from erythrocyte ghosts. Segregation of ATP-utilizing enzymes into smooth membrane. 14 43

To evaluate the mechanism responsible for the effect of deoxycorticosterone acetate (DOCA) on renal Na+-K+-ATPase, we compared the relative contribution of this hormone and of increased absolute sodium reabsorption (TNa) to the restoration of the enzyme in kidneys of adrenalectomized rats. In study A, adrenalectomized animals maintained on a salt-free diet received 5 mg/kg per day DOCA i.m., while sham-operated and untreated adrenalectomized rats receiving the same diet served as controls. Absolute TNa and Na+-K+-ATPase specific activity in the cortex and outer medulla of DOCA-treated rats were similar to those measured in untreated adrenalectomized animals, but were significantly lower than in sham-operated controls. In study B, the adrenalectomized rats did not receive DOCA but were fed a high salt diet and received isotonic saline, 50 ml/kg per day s.c. Absolute TNa and cortical and medullary Na+-K+-ATPase specific activity were significantly higher in the salt-loaded group than in both adrenalectomized and sham-operated rats deprived of salt. These results suggest that absolute sodium reabsorption is a major determinant of renal Na+-K+-ATPase activity, and that the effect of DOCA on this enzyme is secondary to its stimulation of absolute tubular sodium transport.
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PMID:Relationship between mineralocorticoids and renal Na+-K+-ATPase: sodium reabsorption. 14 8

The effects of insulin on monovalent cation transport and on Na-K-ATPase activity from intact cells, tissue homogenates, and purified enzyme of the avian salt gland were studied. Monovalent cation active transport, measured by ouabain-inhibitable 86Rb+ uptake, was significantly increased (21.9 +/- 7.3% SE) in tissue slices exposed to insulin (100 mU/ml) for 15 min. A small but significant (12.2 +/- 1.9%) increase in Na-K-ATPase activity was similarly observed after salt gland tissue slices were exposed to insulin. This increase in enzymatic activity did not occur when broken-cell homogenates were exposed to insulin. Purified preparations of Na-K-ATPase showed no insulin enhancement of activity either in the presence of optimal or less than fully activating Na+ and ATP concentrations. Na-K-ATPase activity was the same in detergent-activated homogenates of both control and insulin-treated slices, consistent with insulin activation of existing enzyme sites. These data support the hypothesis that at least part of the increase in monovalent cation active transport produced by insulin is related to enhanced Na-K-ATPase activity and indicate that the latter phenomenon is dependent on some components or properties of the intact cell.
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PMID:Insulin effects on monovalent cation transport and Na-K-ATPase activity. 14 30


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