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)

The (Na+ +K+)-activated, Mg2+-dependent ATPase from rabbit kidney outer medulla was prepared in a partially inactivated, soluble form depleted of endogenous phospholipids, using deoxycholate. This preparation was reactivated 10 to 50-fold by sonicated liposomes of phosphatidylserine, but not by non-sonicated phosphatidylserine liposomes or sonicated phosphatidylcholine liposomes. The reconstituted enzyme resembled native membrane preparations of (Na+ +K+)-ATPase in its pH optimum being around 7.0, showing optimal activity at Mg2+:ATP mol ratios of approximately 1 and a Km value for ATP of 0.4 mM. Arrhenius plots of this reactivated activity at a constant pH of 7.0 and an Mg2+: ATP mol ratio of 1:1 showed a discontinuity (sharp change of slope) at 17 degrees C, with activation energy (Ea) values of 13-15 kcal/mol above this temperature and 30-35 kcal below it. A further discontinuity was also found at 8.0 degrees C and the Ea below this was very high (greater than 100 kcal/mol). Increased Mg2+ concentrations at Mg2+:ATP ratios in excess of 1:1 inhibited the (Na+ +K+)-ATPase activity and also abolished the discontinuities in the Arrhenius plots. The addition of cholesterol to phosphatidylserine at a 1:1 mol ratio partially inhibited (Na+ +K+)-ATPase reactivation. Arrhenius plots under these conditions showed a single discontinuity at 20 degrees C and Ea values of 22 and 68 kcal/mol above and below this temperature respectively. The ouabain-insensitive Mg2+-ATPase normally showed a linear Arrhenius plot with an Ea of 8 kcal/mol. The cholesterol-phosphatidylserine mixed liposomes stimulated the Mg2+-ATPase activity, which now also showed a discontinuity at 20 degrees C with, however, an increased value of 14 kcal/mol above this temperature and 6 kcal/mol below. Kinetic studies showed that cholesterol had no significant effect on the Km values for ATP. Since both cholesterol and Mg2+ are known to alter the effects of temperature on the fluidity of phospholipids, the above results are discussed in this context.
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PMID:Alterations in phospholipid-dependent (Na+ +K+)-ATPase activity due to lipid fluidity. Effects of cholesterol and Mg2+. 0 90

The adenosinetriphosphatase (ATPase) (EC 3.6.1.3) activity in Azotobacter vinelandii concentrates in the membranous R3 fraction that is directly associated with Azotobacter electron transport function. Sonically disrupted Azotobacter cells were examined for distribution of ATPase activity and the highest specific activity (and activity units) was consistently found in the particulate R3 membranous fraction which sediments on ultracentrifugation at 144 000 X g for 2 h. When the sonication time interval was increased, the membrane-bound ATPase activity could neither be solubilized nor released into the supernatant fraction. Optimal ATPase activty occurred at pH 8.0; Mg2+ ion when added to the assay was stimulatory. Maximal activity always occurred when the Mg2+:ATP stoichiometry was 1:1 on a molar ratio at the 5 mM concentration level. Sodium and potassium ions had no stimulatory effect. The reaction kinetics were linear for the time intervals studied (0-60 min). The membrane-bound ATPase in the R3 fraction was stimulated 12-fold by treatment wiTH TRypsin, and fractionation studies showed that trypsin treatment did not solubilize ATPase activity off the membranous R3 electron transport fraction. The ATPase was not cold labile and the temperature during the preparation of the R3 fraction had no effect on activity; overnight refrigeration at 4 degrees C, however, resulted in a 25% loss of activity as compared with a 14% loss when the R3 fraction was stored overnight at 25 degrees C. A marked inactivation (although variable, usually about 60%) did occur by overnight freezing (-20 degrees C), and subsequent sonication failed to restore ATPase activity. This indicates that membrane reaggregation (by freezing) was not responsible for ATPase inactivation. The addition of azide, ouabain, 2,4-dinitrophenol, or oligomycin to the assay system resulted in neither inhibition nor stimulation of the ATPase activity. The property of trypsin activation and that ATPase activity is highest in the R3 electron transport fraction suggests that its probable functional role is in coupling of electron transport to oxidative phosphorylation.
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PMID:Characterization studies on the membrane-bound adenosine triphosphatase (ATPase) of Azotobacter vinelandii. 0 Jan 41

Nucleotides have at least two functions in eukaryotic cilia and flagella. ATP, originating in the cells, is utilized for motility by energy-transducing protein(s) called dynein, and the binding of guanine nucleotides to tubulin, and probably certain transformations of the bound nucleotides, are prerequisites for the assembly of microtubules. Besides dynein, which can be solubulized from Chlamydomonas flagella as a heterogeneous, Mg2+ or Ca2+-activated ATPase, we have purified and characterized five other flagellar enzymes involved in nucleotide transformations. A homogeneous, low molecular weight, Ca2+-specific adenosine triphosphatase was isolated, which was inhibited by Mg2+ and was not specific for ATP. This enzyme was not formed by treating purified dynein with proteases. It was absent from extracts of Tetrahymena cilia. Its function might be an auxiliary energy transducer, or in steering or tactic responses. Two species of adenylate kinase were isolated, one of which was much elevated in regenerating flagella; the latter was also present in cell bodies. A large part of flagellar nucleoside diphosphokinase activity could not be solubilized. Two soluble enzyme species were identified, one of which was also present in cell bodies. Since these enzymes are of interest because they might function in microtubule assembly, we studied the extent to which brain nucleoside diphosphokinase co-polymerizes with tubulin purified by repeated cycles of polymerization. Arginine kinase was not detected in Chlamydomonas flagellar extracts.
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PMID:Nucleotide-metabolizing enzymes in Chlamydomonas flagella. 0 Mar 97

A member of a family which was known to be susceptible to malignant hyperpyrexia, who was identified as a carrier by the presence of an elevated serum creatine-phosphokinase, has been investigated further. Muscle was examined biochemically, and the study included the sarcoplasmic ATPase-activity, actinomycin, Mg2+ ATPase activity, ATP, phosphocreatine and glucose-6-phosphate. In addition, the calcium uptake by the sarcoplasmic reticulum was studied. The histochemical analysis of the muscle revealed the presence of a new fibre type characterised by a dense rim of ATPase activity, which gives the impression of a 'picture-frame'. Ultramicroscopic study revealed changes in the mitochondria and areas of myofibrillar disruption with swelling of the sarcoplasmic reticulum.
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PMID:'Picture frame' fibres in a carrier of the trait for malignant hyperpyrexia. 0 Jul 95

The optimal conditions are selected for electron-cytochemical detection of the ATPase activity in nuclei of the skeletal muscles of rabbits and nuclei of Vicia faba L. meristem. It is shown that the previous fixation of nuclei in the rabbit skeletal muscle for 10 min in a mixture of the buffer solutions of 4% glutaric dialdehyde and 4% neutral formalin (1:1) causes a decrease in their ATPase activity by 78% in the medium containing Mg2+ and by 34% - in the medium containing Ca2+; in nuclei of horse bean seedlings meristem it lowers respectively by 28 and 16%. Ions of lead in a concentration of 0.4 mM evoke a decrease in the ATPase activity in the medium containing Mg2+, in nuclei of the rabbit skeletal muscles by 35% and in nuclei of horse bean meristem by 15% in the medium containing Ca2+. The vaule of the residual activity is sufficient for detection of the product of ATP enzymic hydrolysis reaction by activity is sufficient for detection of the product of ATP enzymic hydrolysis reaction by the method of electronic cytochemistry. An increase in the Pb2+ concentration higher than 2.8 mM evokes nonenzymic hydrolysis of ATP. The ATPase activity under the electron-cytochemical study is found within the range of pH 6.3-8.5. The product of reaction forms most intensively at pH 7.2-7.5 in the medium with both Mg2+ and Ca2+.
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PMID:[Determination of optimal conditions for the electron-cytochemical detection of ATPase activity in isolated nuclei]. 0 Aug 36

The etioplasts of dark-grown bean leaves showed ATPase (adenosine triphosphatase) activity which had a pH optimum of 8.5, was stimulated by dithiothreitol and unaffected by light-triggering. Bean chloroplasts showed a low activity of dark-induced ATPase with a pH optimum of 8.5 and a substantial amount of light-triggered activity with a pH optimum of 8.0. The light-triggered activity depended on dithiothreitol and Mg2+ and was promoted by phenazine methosulphate. Light-triggered ATPase activity was completely inhibited by 20mum-dicyclohexylcarbodi-imide. Etioplasts developed light-triggered ATPase activity in response to 30 min illumination of the etiolated leaves. During the 48 h of light-induced greening of dark-grown leaves there was a 70% increase of the chloroplast ATPase activity found after light-triggering and a 30% fall in the dark-induced activity, both expressed on a per leaf basis. As the larger part of these changes occurred during the first 30 min of illumination, it is concluded that most or all of the chloroplast ATPase was present in the etioplast, a conclusion identical with that of Lockshin et al. (1971) for maize. During 48 h of greening there was a tenfold increase in the amount of thylakoid membrane in the leaf together with an 83% fall in the ATPase activity per m2 of thylakoid membrane, measured after light-triggering.
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PMID:Plastid development in primary leaves of Phaseolus vulgaris. Development of plastid adenosine triphosphatase activity during greening. 0 Sep 90

1. An activator of the (Ca2+ plus Mg2+)-stimulated ATPase present in the human erythrocytes (membrane) has been isolated in soluble form from hemolysates of these cells. Partial purification has been achieved through use of carboxymethyl-Sephadex chromatography. The resulting activator fraction contained no hemoglobin and only 0.3% of the total adenylate kinase activity of the cell. 2. Whereas the activator was released from erythrocytes subjected to hemolysis in 20 miosM buffer at pH 7.6 or at pH 5.8, only the membranes prepared at pH 7.6 were affected by it. 2. Whereas the activator was released from erythrocytes subjected to hemolysis in 20 miosM buffer at pH 7.6 or at pH 5.8, only the membranes prepared at pH 7.6 were affected by it. 3. When (Ca2+ plus Mg2+)-ATPase activity was measured by 32Pi release from (gamma-32P)ATP, freeze-thawed erythrocytes, as well as membranes prepared at pH 5.8 and at pH 7.6, expressed lower values than noted by assay for total Pi release. When ADP instead of ATP was used as substrate, significant amount of Pi were released by these erythrocyte preparations. Further study revealed (a) production of ATP and AMP from ADP with membranes and hemolysate alone, and (b) exchange of the gamma-and B-position phosphate on (gama-32P)ATP in the presence of membranes plus hemolysates. These observations established the presence of adenylate kinase activity in the (membrane-free) hemolysates and in membranes. It further supports the conclusion that Pi release from ADP by human erythrocytes (freeze-thawed) and by their isolated membranes is due to formation of ATP by adenylate kinase and hydrolysis of this generated ATP by (Ca2+ plus Mg2+)-ATPase. 4. The following points were also established: (a) absence of an ADPase in human erythrocytes; (b) the (Ca2+ plus Mg2+)-ATPase activator enhanced cleavage only of the gama-position of ATP and (c) the (Ca2+ plus Mg2+)-ATPase activator is neither adenylate kinase nor hemoglobin.
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PMID:Studies on an activator of the (Ca2+ plus Mg2+)-ATPase of human erythrocyte membranes. 0 Oct 98

Treatment with neuraminidase decreased the activity of Na+,K+-activated Mg2+-adenosine triphosphatase in plasma membranes isolated from experimental granulation tissue but not that of 5'-nucleotidase or leucine-beta-naphthylamidase. A temporary lowering of the pH of the plasma membrane suspension to 2-3 inactivated all three enzymes, which remained inactive after the pH had been readjusted to 7.4. Addition of dextran preparations to the membrane suspension decreased the activity of adenosine triphosphatase. Ethanol (0.4%) had a similar effect. These marker enzymes of plasma membranes were not affected by additions of hyaluronate, chondroitin sulfate, protein polysaccharide or soluble collagen. Serotonin stimulated the adenosine triphosphatase activity slightly. About 10-20% of the protein in the plasma membrane preparation was extracted with EDTA. This "fuzzy coat" fraction yielded a distinct gel-electrophoretic protein pattern. Hyaluronidase was not helpful in cleaving this surface layer from the plasma membranes.
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PMID:Properties of plasma membranes from granulation tissue with reference to extracellular matrix. 0 56

A simple procedure for the purification of Mg2+-stimulated ATPase of Escherichia coli by fractionation with poly(ethylene glycols) and gel filtration is described. The enzyme restores ATPase-linked reactions to membrane preparations lacking these activities. Five different polypeptides (alpha, beta, gamma, delta, epsilon) are observed in sodium dodecyl sulfate electrophoresis. Freezing in salt solutions splits the enzyme complex into subunits which do not possess any catalytic activity. The presence of different subunits is confirmed by electrophoretic and immunological methods. The active enzyme complex can be reconstituted by decreasing the ionic strength in the dissociated sample. Temperature, pH, protein concentration, and the presence of substrate are each important determinants of the rate and extent of reconstitution. The dissociated enzyme has been separated by ion-exchange chromatography into two major fragments. Fragment IA has a molecular weight of about 100000 and contains the alpha, gamma, and epsilon polypeptides. The minor fragment, IB, has about the same molecular weight but contains, besides alpha, gamma, and epsilon, the delta polypeptide. Fragment II, with a molecular weight of about 52000, appears to be identical with the beta polypeptide. ATPase activity can be reconstituted from fragments IA and II, whereas the capacity of the ATPase to drive energy-dependent processes in depleted membrane vesicles is only restored after incubation of these two fractions with fraction IB, which contains the delta subunit.
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PMID:ATPase of Escherichia coli: purification, dissociation, and reconstitution of the active complex from the isolated subunits. 0 81

A protein has been studied which spontaneously precipitates from stored fractions of platelet soluble phase prepared by density gradient centrifugation. It is rich in a Ca2+ ATPase activity which displays an activity/pH profile resembling that of skeletal muscle myosin. Adjustment of freshly prepared soluble phase fractions to 0.6 M with respect to KCl and dilution 1 in 3 results in the precipitations of a protein fraction with essentially the same enzymatic properties as the spontaneously precipitable protein. These two similar proteins represent between 9 and 13% of the soluble phase total protein and each account for almost the whole of divalent cation activated ATPase activity of the soluble phases from which they were derived. The Mg2+ ATPase activity is only about twice purified with respect to the soluble phase enzyme activity, but the Ca2+ ATPase shows a 10-13-fold enrichment. Synthetic actomyosins can be prepared from the two proteins by addition of either platelet or skeletal muscle actin. These show significant increases in Mg2+ ATPase at the most favourable combination ratios. The ratio between the yield of soluble phase protein obtained by dilution precipitation and the lactate dehydrogenase activity of the soluble phase remains constant under a wide range of homogenization and sonication conditions applied to the original whole platelet suspensions. This confirms our earlier view that the soluble phase is a valid intracellular compartment for a considerable proportion of the platelet contractile protein and that in the complex the myosin-like component predominates.
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PMID:The identification and subcellular localization of thrombosthenin "M", the myosin-like component of pig platelets. 0 43


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