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 influence of an increased temperature (39 degrees C) on a denaturation of 50 kDa-fragment of myosin subfragment 1 was studied in the presence of different nucleoside triphosphates (NTP) and nucleoside diphosphates (NDP). The degree of the denaturation was appreciated evaluated from its trypsinolysis depth. According to their protective influence NTP and NDP were shown to arrange in lines ATP greater than or equal to CTP greater than UTP greater than GTP and ADP greater than GDP greater than CDP greater than UDP, correspondingly. The results received and the literature data allow to suggest that there are at least two states of ATPase site hydrophobic pocket, one of which in responsible for sharp ATPase reaction slowing-down on the stage of macroergic bonding splitting.
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PMID:[Functionally different states of the "hydrophobic pocket" of the myosin ATPase center]. 183 76

Phosphorylase kinase from rabbit skeletal muscle has been found to have an intrinsic ATPase activity that occurs at a rate approximately 0.2% of that of its phosphorylase conversion activity and about three times that of its autophosphorylation activity. The characteristics of this ATPase activity were in all aspects tested essentially the same as the kinase's phosphorylase conversion activity. The ATPase requires Mg2+ and is dramatically stimulated by Ca2+ ions. At neutral pH there is a pronounced lag in the rate of product formation that is not present at alkaline pH, a condition that greatly stimulates both the phosphorylase conversion and ATPase activities. ATP is preferentially hydrolyzed over GTP and the Km for MgATP determined in the ATPase assay is 0.14 mM. ADP, an allosteric activator of phosphorylase conversion, also stimulates the ATPase activity, whereas beta-glycerophosphate, an inhibitor of phosphorylase conversion, is an inhibitor of the ATPase activity. Phosphorylation or partial proteolysis of the kinase, which are known to activate phosphorylase conversion, also activate the ATPase activity. Because the phosphorylase conversion and ATPase activities are regulated in parallel, we conclude that activation of the two catalytic activities must share a common underlying basis, namely an enhanced phosphotransferase activity that is independent of the phosphoryl acceptor.
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PMID:The ATPase activity of phosphorylase kinase is regulated in parallel with its protein kinase activity. 183 56

The purified Ca2+/Mg2+ ATPase from rat heart plasma membrane was activated by Ca2+ and Mg2+ with Ka values of 1.47 mM and 2.51 mM, respectively; other divalent cations also activated the enzyme but to a lesser extent. Divalent cations like Cu2+, Zn2+, Ni2+, Cd2+ were potent inhibitors of the enzyme activity in the presence of Ca2+ or Mg2+ whereas Na+, K+ or HCO3- did not affect the Ca2+/Mg2+ ATPase activity; the pH optima was 8.5. The enzyme hydrolyzed ATP with a Km of 0.34 mM for Ca2+ ATPase and 0.48 mM for Mg2+ ATPase; various nucleoside triphosphate such as ITP, CTP, GTP, and UTP were also hydrolyzed. Phospholipase A and C as well as neuraminidase decreased the Ca2+/Mg2+ ATPase activity whereas phospholipase D was ineffective. The purified Ca2+/Mg2+ ATPase was found to bind ATP-r-35S with two affinities; the KD values were 50.9 +/- 0.8 and 1160 +/- 198 nM and the Bmax values were 8.71 +/- 0.16 and 145 +/- 9.7 nmol/mg protein for high and low affinity sites, respectively. Treatment of the enzyme preparation with phospholipases and neuraminidase did not affect the ATP-r-35S binding. Ca2+ was also found to bind with Ca2+/Mg2+ ATPase with a KD of 0.384 mM and a Bmax of 1.85 mumol/mg protein; Ni2+, Mn2+, Zn2+ at 1 mM concentrations inhibited the Ca2+ binding but Mg2+ and verapamil were without effect. Phospholipase A and neuraminidase decreased the Ca2+ binding by 20-30%; this indicated that Ca2+ binding with the purified enzyme may be partly due to the phospholipids and sialic acid residues associated with the enzyme. These results show that the purified Ca2+/Mg2+ ATPase is a Ca2+ binding glycoprotein having two binding sites for ATP. Furthermore, this study suggests that phospholipids associated with purified Ca2+/Mg2+ ATPase are required for maximal activity.
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PMID:Characterization of the purified rat heart plasma membrane Ca2+/Mg2+ ATPase. 183 90

Ouabain- and furosemide-insensitive and ATP-dependent Cl- uptake was demonstrated in rat renal membrane vesicles. Such a Cl- uptake activity was prominent in cortical plasma membrane fractions with high activities of Cl(-)-ATPase and Na+, K(+)-ATPase. The membrane vesicles accumulated Cl- in an osmotically reactive manner with the following sequence of nucleotide specificity: ATP greater than ITP greater than UTP greater than GTP greater than CTP., beta, gamma-Methylene ATP, ADP and AMP had no effect. ATP-dependent Cl- uptake was markedly inhibited by a Cl(-)-ATPase inhibitor, ethacrynic acid (0.3 mM), but not affected by an H(+)-ATPase inhibitor, N,N'-dicyclohexylcarbodiimide (0.1 mM). These findings suggest that an ethacrynic acid-sensitive and ATP-driven
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PMID:Ethacrynic acid-sensitive and ATP-dependent Cl- transport in the rat kidney. 183 37

Simian virus 40 large T antigen is a helicase separating the complementary strands of double-stranded DNA in the presence of hydrolyzable ATP and of double-stranded RNA in the presence of non-ATP nucleotides (GTP, CTP or UTP). We have constructed partially single-stranded nucleic acid substrates consisting of RNA or DNA strands hydrogen bonded to either RNA or DNA complements. We found that ATP is utilized as a cofactor for the T-antigen-catalyzed unwinding reaction when the substrates contain overhanging single-stranded DNA, regardless of whether the double-stranded region is DNA or hybrid DNA.RNA. Conversely, non-ATP nucleotides are used when the overhanging single strand is RNA. Based on these and additional findings, we propose that the bound nucleic acid induces a conformational change in T antigen resulting in a proper orientation of both nucleic acid and nucleotide relative to the active center of the ATPase/helicase domain of the enzyme. The implications of our conclusion for the roles which T antigen may play in vivo are discussed.
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PMID:Simian-virus-40 large-T-antigen-catalyzed DNA and RNA unwinding reactions. 184 11

We have studied the mechanism by which liver Golgi apparatus maintains the acidity of its contents, using a subcellular fraction from rat liver highly enriched in Golgi marker enzymes. Proton accumulation (measured by quenching of acridine-orange fluorescence) and anion-dependent ATPase were characterized and compared. Maximal ATPase and proton accumulation required ATP; GTP and other nucleotides gave 10% to 30% of maximal activity. Among anions, Cl- and Br- approximately doubled the activities; others were much less effective. Half-maximal increase of ATPase and H+ uptake required 55 mmol/L and 27 mmol/L Cl-, respectively. In predominantly chloride media, SCN- and NO3- markedly inhibited H+ uptake. Nitrate competitively inhibited both the chloride-dependent ATPase (apparent Ki 6 mmol/L) and proton uptake (apparent Ki 2 mmol/L). Nitrate and SCN- also inhibited uptake of 36Cl. Replacing K+ with Na+ had no effect on the initial rate of proton uptake but somewhat reduced the steady state attained. Replacement of K+ with NH4+ and choline reduced proton uptake without affecting ATPase. The ATPase and H+ uptake were supported equally well by Mg2+ or Mn2+. The ATPase was competitively inhibited by 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid (apparent Ki 39 mumol/L). Other agents inhibiting both H+ uptake and ATPase were N-ethylmaleimide, N,N'-dicyclohexylcarbodiimide, chlorpromazine, diethylstilbestrol, Zn2+, Co2+ and Cu2+. In the Cl- medium, accumulated protons were released by ionophores at the relative rates, monensin = nigericin greater than valinomycin greater than carbonyl cyanide mchlorophenylhydrazone; the last of these also reduced ATPase activity. In the absence of Cl-, monensin and valinomycin both stimulated the ATPase. These results show a close association between ATPase activity and acidification of liver Golgi vesicles. They support a role for Cl- that depends on its uptake as a counter ion for H+ and suggest that it may also stimulate proton transport by a more direct effect on a component of the transport system.
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PMID:Proton accumulation and ATPase activity in Golgi apparatus-enriched vesicles from rat liver. 184 95

Na, K-ATPase and Mg-ATPase activities were measured in the synaptosomes of the temporal auditory projection area and the frontal association area. Moreover, the effects of carbacholine and serotonin on those activities were investigated. Na, K-ATPase activity in the synaptosomes of the association area was shown to be reliably higher that in the synaptosomes of the projection area (11.02 +/- 0.45 vs 8.40 +/- 0.55 microM Pi/mg of protein hr; P less than 0.05). Mg-ATPase activity was higher in the second case as compared to the first one (11.40 +/- 0.38 vs 9.04 +/- 0.35; p less than 0.05). Carbacholine and serotonin (10(-8)-10(-3) M) were found to induce equal inhibition of Na, K-ATPase activity in the synaptosomes of both cortices (1 max = 25-30%, 1C50 = 0.2-0.3 microM) which is blocked respectively with atropine (10(-6) M) and methysergide (10(-6) M) and enhanced in presence of GTP (5.10(-5) M). The enzyme activity is also inhibited by the non-hydrolysable guanine nucleotide, GTP gamma S (10(-8)-10(-4) M), in the absence of the antagonists (1 max = 35-40%, 1 C50 = 0.02 microM). In the methysergide-containing medium serotonin exerts a dose-dependent stimulatory effect on Na, K-ATPase which is more pronounced in the synaptosomes of the association area (A max = 25%, A C50 = 0.05 microM). Mg-ATPase activity of membrane preparations is liable to be stimulated by both serotonin and carbacholine, stimulation being more pronounced in the synaptosomes of the association cortex as well (A max = 35%, A C50 = 0.2-0.3 microM). This effect is insensitive either to the antagonists of the corresponding receptors or to GTP. GTP gamma S does not cause alterations in the enzymatic activity. Na, K-ATPase is suggested to be coupled to muscarine and serotonin receptors in the synaptic membranes of both projection and association cortical areas via a GTP-binding protein. At the same time, the agonists of receptors mentioned above are presumably also capable to effect Mg-ATPase activity by the receptor-independent way.
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PMID:[Effect of carbacholine and serotonin on the ATPase activity in synaptosomes of the projection and association areas of the feline cerebral cortex]. 185 44

Permeabilized endothelial cell monolayers retracted on exposure to ATP and Ca2+. ADP, inosine triphosphate (ITP), GTP, adenosine 5'-(gamma-thio)triphosphate (ATP-gamma S), and 5'-adenylylimidodiphosphate failed to support retraction. However, ATP gamma S, a substrate for myosin light-chain kinase (MLCK) but not myosin adenosinetriphosphatase (ATPase), combined with ITP, a substrate for myosin ATPase but not MLCK, supported retraction. Two MLCK pseudosubstrate peptides, M5 and SM-1, inhibited endothelial cell retraction equally and more effectively than myosin kinase-inhibitory peptide with a sequence based on the phosphorylated site of myosin light chain. M5 was shown to inhibit thiophosphorylation of endothelial cell myosin light chains. Endothelial cells incubated with exogenous unregulated kinase in the presence of ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetra-acetic acid retracted on addition of ATP. This retraction was accompanied by thiophosphorylation of the 19 kDa myosin light chains in the presence of ATP gamma 35S. The N-ethylmaleimide-modified subfragment 1 of myosin heads, a specific inhibitor of actin-myosin interaction, prevented retraction. These data add support to the proposal of a central role for MLCK activation of myosin in endothelial retraction.
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PMID:Regulation of permeabilized endothelial cell retraction by myosin phosphorylation. 185 58

The molecular mechanisms surrounding the toxicity and high mortality rate that accompany the release of bacterial lipopolysaccharide (LPS) are unclear, although its potent activity suggests that an amplification system is involved. Because previous studies suggest that a guanine-nucleotide-binding protein (G-protein) may participate in LPS action, we have evaluated the effects of LPS on GTPase activity in membranes isolated from macrophage (RAW 264.7) and fibroblast (B82L) cell lines. LPS induced substantial GTPase activation (200-300% above basal), and kinetic analyses indicated that the maximal LPS-stimulated increase in velocity is observed within 15 min, that it is a low-Km (for GTP) activity, that it can be enhanced by ammonium sulphate, and that it appears to be pertussis toxin-insensitive. Moreover, the LPS-enhanced GTPase activity was not antagonized by phosphatase/ATPase inhibitors such as p-nitrophenyl phosphate, ouabain, bafilomycin or N-ethylmaleimide, and in fact was potentiated by the addition of ATP or ADP. Conversely, the LPS precursor, lipid X, which can decrease the lethal effects of LPS, was found to dose-dependently inhibit the LPS-mediated stimulation of GTPase activity. Half-maximal inhibition was seen at the same lipid X/LPS ratio known to be effective in vivo, i.e. 1:1(w/w). These effects appear to be specific because other phospholipids, detergents and glycosides neither stimulated basal, nor inhibited LPS-induced, GTPase activity. These data suggest the involvement of a GTPase in LPS action, and indicate that lipid X may act to directly antagonize LPS at this level.
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PMID:Bacterial lipopolysaccharide-stimulated GTPase activity in RAW 264.7 macrophage membranes. 185 66

The relationships between agonist-sensitive calcium pools and those discharged by the Ca(2+)-ATPase inhibitor thapsigargin were studied in intact bovine adrenal glomerulosa cells and a subcellular adrenocortical membrane fraction. In Fura-2-loaded glomerulosa cells, angiotensin II (AII) stimulated a rapid increase in cytoplasmic Ca2+ concentration ([Ca2+]i) followed by a smaller plateau phase that was dependent on extra-cellular Ca2+. In such cells thapsigargin caused a sustained and dose-dependent increase in [Ca2+]i which was diminished in Ca(2+)-deficient medium. The contribution of an influx component to the thapsigargin-induced [Ca2+]i response was demonstrated by measurement of 45Ca influx rate in glomerulosa cells. Thapsigargin-induced Ca2+ entry was significantly less than that evoked by AII, and its kinetics were similar to those of the concomitant increase in [Ca2+]i. The rate of emptying of the agonist-responsive Ca2+ pool after thapsigargin treatment, as indicated by the progressive decrease in the size of the AII-induced Ca2+ transient, showed a rapid initial (t1/2 = 1.7 min) component that accounted for about 80% of the response and a slowly decreasing phase with t1/2 = 112 min. The latter thapsigargin-resistant component was abolished by the removal of extracellular Ca2+. Pretreatment with AII dose-dependently attenuated but did not abolish the subsequent Ca2+ response to thapsigargin and also increased the rate of the Ca2+ rise induced by thapsigargin. In bovine adrenocortical microsomes, thapsigargin inhibited the ATP-dependent filling of Ca2+ pools and caused a dose-dependent rise in extravesicular Ca2+ levels when added to previously loaded microsomes. The thapsigargin-releasable Ca2+ pool in adrenal microsomes was larger than the inositol 1,4,5-trisphosphate (Ins(1,4,5)P3)-sensitive Ca2+ pool but only slightly greater than the GTP-releasable pool. Ins(1,4,5)P3-induced Ca2+ release was reduced markedly when ATP-dependent Ca2+ loading of the microsomes was prevented by prior addition of thapsigargin. However, the subsequent Ca2+ response to Ins(1,4,5)P3 was consistently better preserved after the addition of thapsigargin to microsomes preloaded with Ca2+. This difference suggests that although Ca2+ uptake by the Ins(1,4,5)P3-responsive pool is also sensitive to thapsigargin, once filled, this pool shows a slower passive leakage than other thapsigargin-sensitive pools. These findings indicate that thapsigargin increases [Ca2+]i by inhibiting Ca2+ uptake into multiple intracellular Ca2+ pools and by also promoting entry of extracellular Ca2+.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Relationship between agonist- and thapsigargin-sensitive calcium pools in adrenal glomerulosa cells. Thapsigargin-induced Ca2+ mobilization and entry. 191 86


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