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)

It is found that dinitrophenol, octanol and toluene produce similar effects on pH-dependence of ATPase of myosin and heavy meromyosin (HMM), i.e. they decrease or remove the neutral suppression of ATPase activity. The appearance of pH-dependence curves is simplified and approaches the form, which is characteristic for the ionisation curve of one; in the last resort two groups, participating in the enzyme activity. The activity of HMM is higher and the zone of the neutral suppression is diminished at low ionic strength, the activation by the modifiers being observed at the significantly lesser degree. CaATPase activation by dinitrophenol, octanol and toluene is suggested to be of the same nature and is accounted for the masking of "the inhibiting" ionizable group of the enzyme with near to neutral pK. This masking may be the result of the conformational changes occuring at the deformation of hydrofobic regions. The ionization of "the activity inhibiting" group of the enzyme depends directly or indirectly on the concentration of potassium chloride and the increase of KCl concentration bring to the inhibition of ATPase activity.
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PMID:[Influence of dinitrophenol, octanol and toluene upon pH-dependence of ca-ATPase activity of heavy meromyosin]. 1 25

Rat liver lysosomes were lysed and subfractionated by differential centrifugation through 0.2M-NaCl to yield a membranous pellet. This membrane fraction contains less than 20% of the lysosomal protein, adenosine triphosphatase activity of about 1.2mumol/min per mg of protein, 120nmol of thiol groups/mg of protein and at least 16 protein and glycoprotein bands on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The gel patterns of membranes isolated from lysosomes after treatment with (1) [125I]iodidehydrogen peroxide-lactoperoxidase, (2) toluene 2,4-di-isocyanate-activated bovine serum albumin, (3) trypsin and (4) subtilisin indicate that most of the membrane proteins are exposed to the cytoplasm. These exposed proteins are candidates for intracellular receptors which recognize either substances that are to be degraded or vesicles containing those substances.
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PMID:Properties of the membrane proteins of rat liver lysosomes. The majority of lysosomal membrane proteins are exposed to the cytoplasm. 15 36

1. The distribution of ATPase and several marker enzymes was examined after differential and sucrose gradient centrifugation of yeast homogenates. 2. An ATPase activity not sensitive to oligomycin is found exclusively associated with a particulate fraction equilibrating at densities of 1.23-1.25. This particulate material shows the chemical and enzymatic characteristics of the yeast plasma membrane. 3. The pH optimum of the plasma membrane ATPase is 5.6, as compared with 8.5 for the mitochondrial ATPase. In addition to oligomycin, the enzyme is not sensitive to other inhibitors of the mitochondrial ATPase as azide, dicyclohexylcarbodiimide and the mitochondrial ATPase inhibitor protein. It is inhibited by p-chloromercuryphenyl sulfonate, fluoride, quercetin and by the antibiotic Dio-9 but is not affected by ouabain. 4. The plasma membrane ATPase shows a high affinity for ATP (Km = 0.1 mM) and is very specific for this compound, hydrolyzing other nucleotide triphosphates less than 25% as rapidly. No activity was detected with ADP. 5. The enzyme requires a divalent cation for activity and Mg2+ is the most effective. It is not significantly stimulated by K+ or bicarbonate and Ca2+ is inhibitory. 6. The activity cannot be assayed in intact cells unless they are permeabilized with toluene. This suggest that the active site is on the cytoplasmic side of the plasma membrane.
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PMID:Characterization of the plasma membrane ATPase of Saccharomyces cerevisiae. 15 59

Effect of platinum and palladium complexes on respiration and ATPase activity in bovine heart tissue as well as on respiration of submitochondrial particles was studied. The highest inhibitory activity was exhibited by the complexes of platinum and palladium with pi-ligands in internal coorhdinational sphere such as ethylene-C H4, norbornadiene-C7H8 and allyl-C3H5. The electron density at the central atom of the complex was not responsible for the inhibitory affect of platinum and palladium on mitochondria.
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PMID:[Effect of platinum and palladium compounds on mitochondrial enzymatic systems]. 15 83

Rabbit antiserum against highly purified reaction center preparations was shown to react specifically with a single component of chromatophore membranes from Rhodopseudomonas spheroides strain R-26. The conjugate of purified gamma globulin and ferritin prepared with toluene diisocyanate was used to determine the localization of reaction centers in the chromatophore membranes. Virtually no antibody was bound by intact membranes. After removing the 9nm ATPase from these membranes by dilute EDTA treatment, a considerable amount of antibody was bound to the exposed outer membrane surface. The reaction center binding sites were estimated to be uniformly distributed with approx. 1 reaction center per 200 nm-2 of membrane surface. These results indicate that the reaction centers are located near the outer membrane surface but below the ATPase particles. Since the distribution of reaction centers and particles on rough faces seen by freeze-fracture particle may be a complex of a reaction center and other electron transfer components localized within the hydrophobic region of the membrane.
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PMID:Localization of photosynthetic reaction centers by antibody binding to chromatophore membranes from Rhodopseudomonas spheroides strain R26. 80 32

The effects of toluene and n-hexane on rat synaptosomal membrane fluidity and the integral enzymes acetylcholinesterase (AChE) and ATPase were studied in vitro. The synaptosome membranes were isolated in Percoll and sucrose gradients. After adding toluene and n-hexane to the incubation mixture (37 degrees) in 2,4,6 and 8 mM concentrations, the fluidity changes were measured by the lateral pyrene diffusion method from Percoll-isolated membranes, and the ATPase and acetylcholinesterase activities were determined from both synaptosome isolations. Addition of toluene caused a linearly correlated increase of the synaptosomal membrane fluidity and a linear decrease of the AChE activity. The ATPase activity did not decrease linearly but dose-dependently. In contrast to the effects of toluene in vitro, addition of n-hexane in the same concentration range had no comparable influence on membrane fluidity nor on the activities of both integral enzymes despite its even higher lipid/water partition coefficient. Toluene increases synaptosomal membrane fluidity and at the same time inhibits the integral enzymes, probably by disturbing the lipid/protein interaction.
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PMID:Effects of toluene and n-hexane on rat synaptosomal membrane fluidity and integral enzyme activities. 144 47

The effect of simultaneous exposure of rats to toluene and ethanol on synaptosomal calcium uptake and (Ca2+/Mg2+)-ATPase activity was studied. Rats were exposed to 500 p.p.m. toluene by inhalation for 12 hr a day during four weeks. During the exposure period, the rats had access to 5% sucrose solution containing 20% ethanol or to 5% sucrose solution alone. Rats drinking ethanol exhibited a smaller weight gain than rats drinking water alone. Furthermore, rats exposed simultaneously to toluene and ethanol had a higher ethanol intake than unexposed rats. The toluene exposure caused a higher synaptosomal calcium uptake in vitro. Ethanol intake did not change the synaptosomal calcium uptake in vitro. The synaptosomal calcium uptake in rats exposed to toluene and ethanol was nearly identical to that measured in control rats. In vivo exposure to toluene, or ethanol, or toluene/ethanol simultaneously did not affect the (Ca2+/Mg2+)-ATPase activity in vitro. Incubation with toluene in vitro decreased the (Ca2+/Mg2+)-ATPase activity in a concentration dependent manner. Ethanol had only a slight effect on the enzyme. Simultaneous incubation with toluene and ethanol showed an antagonistic effect of ethanol on the toluene inhibition of the ATPase activity.
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PMID:Effects of simultaneous ethanol and toluene exposure on nerve cells measured by changes in synaptosomal calcium uptake and (Ca2+/Mg2+)-ATPase activity. 183 26

A system composed of toluene, phospholipids, and Triton X-100 in which the ATPase activity of bovine heart submitochondrial particles can be studied at low water concentrations and high temperatures is described. In this system, ATPase activity starts to appear at 0.5% (v/v) water and increases as the concentration of water is increased. At 3.8% water, the enzyme exhibits saturation kinetics with respect to Mg-ATP with a Km similar to that observed in an all-water system (approximately 300 microM), but the Vmax is about 100 times lower (6 nmol min-1 mg-1) than that in water. At concentrations of water between 0.5% and 2%, the enzyme catalyzes ATP hydrolysis at temperatures of up to 91 degrees C. The conditions for achieving catalysis at high temperatures are described. Even though at low water concentrations the enzyme catalyzes ATP hydrolysis at temperatures significantly higher than in totally aqueous media, the optimal temperature for hydrolysis (approximately 58 degrees C) is independent of the water content. The half-life of the enzyme at high temperatures is significantly higher at low water concentrations than in aqueous media. In the system described, the enzyme is located in a compartment distinct from that of the substrate and products of the reaction. Apparently, the enhancement of catalytic rates by water is due to a higher conformational mobility of the protein; the same factor causes a decrease in the thermostability of the enzyme.
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PMID:Enzyme catalysis in organic solvents with low water content at high temperatures. The adenosinetriphosphatase of submitochondrial particles. 214 55

The mechanism by which toluene decreased synaptosomal phosphatidylethanolamine (PE) was investigated by studying degradative and synthetic phospholipid pathways. Toluene stimulated a PE-specific phospholipase (PLase) C both in vivo (44-75%) and in vitro (20-30%) whereas PLase A, PLase D and base exchange enzymes were unchanged. Toluene, in vivo, also increased the synthesis of PE (27%) when expressed as [3H]ethanolamine incorporation into [3H]PE, but had no effect on PE synthesis when administered in vitro. Perhaps this reflects a compensatory mechanism in synaptosomes to replace PE via increasing de novo synthesis. Phospholipid methylation, an event proposed to be related to the transduction of singals across membranes, as well as a measure of membrane function, was studied. Toluene was found to rapidly increase phospholipid methylation (43%, 15 min), followed by a significant decrease (35%, 1 hr). Another measure of membrane, as well as cell function used in these studies was ATPase activity. Toluene, both in vivo and in vitro, stimulated Na+, K(+)-adenosine triphosphatase (ATPase) activity (20-30%, 15-30 min), whereas Mg(++)-ATPase and Ca(++)-ATPase were unaffected, an indication that toluene alters neuronal cell function. Membrane fluidity studies using fluorescence polarization reported that toluene, both in vivo and in vitro, increased the outer synaptosomal membrane fluidity using the probe trimethylammonium-diphenylhexatriene, whereas no effect was observed on the central core fluidity using diphenylhexatriene. These are the first studies to demonstrate that an organic solvent effects only specific membrane region fluidities. One possibility is that early synaptic alterations resulting from toluene exposure may be preceded by increases in outer membrane fluidity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Altered synaptosomal phospholipid metabolism after toluene: possible relationship with membrane fluidity, Na+,K(+)-adenosine triphosphatase and phospholipid methylation. 216 49

The effect of toluene on the central nerve system was studied by using rat brain synaptosomal membranes as in vitro and in vivo models. The activity of Ca2+/Mg2+ ATPase and the membrane fluidity were determined. Short-term exposure in vivo to 500 p.p.m. of toluene had an inhibitory effect on the enzyme studied whereas long-term exposure to toluene caused an increased activity. Exposure to toluene had no effect at all on the membrane fluidity. The in vitro experiment showed an effect of toluene on both parameters. The alteration in the enzyme activity and membrane fluidity was parallel in the exposed animals as well as those of control. Our results show that long-term exposure to toluene affects nerve cell membranes by other mechanisms than those observed under in vitro conditions.
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PMID:The effect of toluene exposure for up to 18 months (78 weeks) on the (Ca2+/Mg2+)ATPase and fluidity of synaptosomal membranes isolated from rat brain. 253 May 6


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