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)

An abnormal flux of monovalent cations may be related to the epileptogenic process in man. One possible mechanism for deranged electrolyte metabolism in epileptic brain is an abnormality in sodium, potassium-dependent adenosine triphosphatase (Na, K ATPase). We found the activity of Na, K ATPase to be significantly less in epileptic human corfex than in nonepileptic cortex. Histological changes have been simultaneously evaluated in epileptic brain. A second membrane-bound enzyme, acetylcholinesterase (AChE), was also assayed as a marker for neuronal membranes and found not to correlate with the epileptogenicity of human brain. In addition, the concentrations of the anticonvulsant compound phenytoin have been determined in the serum and cerebral cortex of epileptic and nonepileptic patients. The ratio of phenytoin in cortex to serum concentration is significantly lower in epileptic patients than in nonepileptic controls.
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PMID:Human epileptic brain Na, K ATPase activity and phenytoin concentrations. 12 76

The lipid composition of yeast cells was manipulated by the use of an unsaturated fatty acid auxotroph of Saccharomyces cerevisiae. There was a 2-3-fold decrease in the concentration of cytochromes a+a3 when the unsaturated fatty acid content of the cells was decreased from 60-70% of the total fatty acid to 20-30%. The amounts of cytochromes b and c were also decreased under these conditions, but to a lesser extent. Further lipid depletion, to proportions of less than 20% unsaturated fatty acid, led to a dramatic decrease in the content of all cytochromes, particularly cytochromes a+a3. The ATPase (adenosine triphosphatase), succinate oxidase and NADH oxidase activities of the isolated mitochondria also varied with the degree of unsaturation of the membrane lipids. The lower the percentage of unsaturated fatty acid, the lower was the enzymic activity. Inhibition of mitochondrial ATPase by oligomycin, on the other hand, was not markedly influenced by the membrane-lipid unsaturation. Npn-linear Arrenius plots of mitochondrial membrane-bound enzymes showed transition temperatures that were dependent on the degree of membrane-lipid unsaturation. The greater the degree of lipid unsaturation, the lower was the transition temperature. It was concluded that the degree of unsaturation of the membrane lipids plays an important role in determining the properties of mitochondrial membrane-bound enzymes.
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PMID:Membrane-lipid unsaturation and mitochondrial function in Saacharomyces cerevisiae. 12 85

1. The uptakes of Pi and serine by whole cells of mutant strains of Escherichia coli K12, grown under both aerobic and anaerobic conditions, were studied. 2. Uptake by aerobic cells was low in a ubiquinone-less mutant but normal in two mutant strains unable to couple phosphorylation to electron transport. 3. One of these uncoupled strains, carrying the unc-405 allele, does not form a membrane-bound Mg2+-stimulated adenosine triphosphatase aggregate, and it is concluded that the Mg2+-stimulated adenosine triphosphatase does not serve a structural role in the aerobic active transport of Pi or serine. 4. The other uncoupled strain, in which aerobic uptake is unaffected, carries a mutation in the uncB gene, thus distinguishing this gene from the etc gene, previously shown to be concerned with the coupling of electron transport to active transport. 5. The uptakes of Pi and serine by anaerobic cells were normal in the ubiquinone-less mutant, but defective in both the uncoupled strains. 6. The uptake of Pi and serine by anaerobic cells of the uncB mutant could be increased by the addition of fumarate to the uptake medium. The unc-405 mutant, however, required the addition of fumarate for growth and for uptake. 7. The uncB mutant, unlike the unc-405 mutant, is able to grow anaerobically in a minimal medium with glucose as sole source of carbon. Similarly a strain carrying a mutation in the frd gene, which is the structural gene for the enzyme fumarate reductase, is able to grow anaerobically in a glucose-minimal medium. However, a mutant strain carrying mutations in both the uncB and frd genes resembles the unc-405 mutant in not being able to grow under these conditions.
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PMID:Metabolite transport in mutants of Escherichia coli K12 defective in electron transport and coupled phosphorylation. 12 86

It is shown that uncouplers inhibit the incorporation of catecholamines by vesicles of chromaffin granules in parallel with their stimulatory effect on the membrane-bound adenosine triphosphatase.
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PMID:The effect of uncouplers on catecholamine incorporation by vesicles of chromaffin granules. 12 89

The membrane-bound coupling factor from Mycobacterium phlei was solubilized from membrane vesicles by washing with low ionic strength buffer or 0.25 M sucrose. The solubilized enzyme exhibited coupling factor, latent ATPase, and succinate oxidation-stimulating activity. Purification by affinity chromatography using Sepharose coupled to ADP yielded a homogeneous preparation of latent ATPase which was purified about 200-fold with an 84% yield in a single step. Purified latent ATPase exhibited coupling factor activity but no succinate oxidation-stimulating activity. The molecular weight of latent ATPase was determined to be 250,000 +/- 10,000 by Sephadex G-200 chromatography. The ATPase was unmasked by trypsin treatment and activated by Mg2+ ion. However, trypsin treatment inactivated the coupling factor activity in the purified enzyme, indicating that the catalytic sites for ATPase and coupling activity are different. Unlike mitochondrial ATPase, latent ATPase from M. phlei was not cold-labile. Of the nucleoside triphosphates, UTP, ITP, and epsilon-ATP (1-N6-ethenoadenosine triphosphate) were hydrolyzed to a lesser extent compared to ATP. Kinetic data showed that ADP acted as a competitive inhibitor of latent ATPase activity with a Ki of 5 x 10(-3) M. Uncouplers of oxidative phosphorylation and respiratory inhibitors did not affect the latent ATPase activity, while sodium azide (0.1 mM) inhibited the latent ATPase activity.
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PMID:Energy-transducing membrane-bound coupling factor-ATPase from Mycobacterium phlei. I. Purification, homogeneity, and properties. 12 54

Delta1-tetrahydrocannabinol was found to be a potent inhibitor of some membrane-bound enzymes, such as Mg-ATPase, Na-K-ATPase and acetylcholinesterase. At a given concentration, the degree of inhibition varied for each enzyme; the inhibition was more pronounced for the enzymes that are parts of the membranes. As the kinetic parameters of these enzymes are functions of the membrane composition and organization, these parameters were studied in vitro in the presence of THC. Although the Mg-ATPase was inhibited by THC, there was no change in the allosteric behaviour of the enzyme, indicating that the alterations caused by THC did not affect the enzymatic structure. The Na-K-ATPase and acetylcholinesterase had a different allosteric behaviour as compared to controls; these modifications were like the alterations caused by the decrease in membrane fluidity. These results suggest the fact that THC is incorporated in the membranes and causes alterations in the physical organization of the membranes.
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PMID:Alteration of membrane integrity by delta1-tetrahydrocannabinol. 12 14

The diazido derivative of ethidium bromide has been synthesized as a potential photoaffinity label and shown to be at least as effective as a mitochondrial mutagen as the parent compound, with a similar mode of action. Exposure of mitochondria of Saccharomyces cerevisiae to the compound, followed by ultraviolet-irradiation, which converts it to the highly reactive dinitrene, results in its specific binding to a single component which has been tentatively identified as the smallest polypeptide (subunit 9) of the membrane-bound ATPase. An analogus reaction is also obtained with the soluble, oligomycin-sensitive ATPase complex but not with the F1-ATPase itself. The reaction with the ATPase complex can also be monitored by fluorescence enhancement and by this attribute, as well as by other criteria, diazido-ethidium bromide, ethidium bromide itself, euflavine, N,N'-dicyclohexylcarbodiimide, 2,4-dinitrophenol, and 2-azido-4-nitrophenol all appear to compete for the same, lipophilic, binding site. A mitochondrial mutation (73/1) (see Flury, U., Feldman, F., and Mahler, H.R. (1974) J. Biol. Chem. 249, 6630-6637) produces a photoaffinity product with an altered electrophoretic mobility and molecular weight.
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PMID:Use of diazido ethidium bromide as a specific probe for mitochondrial functions. 12 40

In crude extracts of T2L phage-infected Escherichia coli cells an enzyme activity was found that produced poly(A) from ATP as substrate. Purification of the extract led to the isolation of two enzymes, a polynucleotide phosphorylase and an ATPase. The polynucleotide phosphorylase possessed the same properties as the well-known enzyme from uninfected cells and its molecular weight was about 265 000. The ATPase was purified to over 90% purity; its molecular weight was estimated to be about 165 000 with three subunits of 55 000. The characterization of this enzyme showed that it was different from any ATPase known so far. Mg2+ cannot be replaced by Ca2+, as it can from the membrane-bound ATPases. The only product yielded by the enzyme was ADP; it was very specific for ATP, other ribonucleotide triphosphates being practically unaffected. The rate of ATP splitting was found to be very high, the turnover number being 2.51 X 10(4) min-1 at 37 degrees C. Even at 0 degree C the enzyme was still active. The optimal assay conditions for ATPase turned out to be very similar to those of polynucleotide phosphorylase. Thus the combination of the two enzymes very efficiently produced poly(A) from ATP. In this combination the polynucleotide phosphorylase was the rate-limiting enzyme, since its turnover number was about 40 times lower than that of the ATPase. The evaluation of a variety of properties of the poly(A)-synthesizing constituent found in the crude extracts led us to conclude that this activity arises from the combined action of ATPase and polynucleotide phosphorylase, and is not due to a poly(A) polymerase.
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PMID:Poly(A) synthesis in T2L phage-infected Escherichia coli. A combination of polynucleotide phosphorylase and ATPase. 12 62

1. [3H]ouabain binding to human erythrocyte membranes is a time- and temperature-dependent process. The association of ouabain to the membrane-bound receptor follows second-order kinetics, while the dissociation is a monomolecular reaction. An association rate constant of 4-6 x 10(4) M-1 sec-1 and a dissociation rate constant of 1-4 x 10(-4) sec-1 were measured at 37 degrees C. The dissociation constant calculated from these data agrees with that determined from equilibrium binding experiments. There is only one type of ouabain binding sites with high affinity for the drug as reflected by the low dissociation constant of 0-28 x 10(-8) M. 2. The dissociation constants of the ouabain-receptor complexes from human erythrocyte and cardiac membranes are identical. 3. The maximal number of membrane-bound ouabain binding sites was measured from equilibrium binding experiments as 288 +/- 28 per single erythrocyte. Thus one receptor site corresponds to less than 1 mum2 of the membrane, provided the receptors are diffusely distributed on the surface of the membrane. 4. Neither the maximal number of ouabain receptors nor the affinity for the drug changes with the age or sex of the blood donor. 5. A maximal transport capacity for sodium of 5-6 m-equiv/hr.1. is calculated from the number of receptor sites per erythrocyte and from the turn-over number of the (Na+ + K+)-ATPase.
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PMID:Quantitative aspects of ouabain binding to human erythrocyte and cardiac membranes. 12 37

We have partially purified active delta and epsilon subunits of the E. coli membrane-bound Mg2+-ATPase (ECF1). Treating purified ECF1 with 50% pyridine precipitates the major subunits (alpha, beta, and gamma) of the enzyme, but the two minor subunits (delta and epsilon), which are present in relatively small amounts, remain in solution. The delta and epsilon subunits were then resolved from one another by anion exchange chromatography. The partially purified epsilon strongly inhibits the hydrolytic activity of ECF1. The epsilon fraction inhibits both the highly purified five-subunit ATPase and the enzyme deficient in the delta subunit. The latter result indicates that the delta subunit is not required for inhibition by epsilon. By contrast, two-subunit enzyme, consisting chiefly of the alpha and beta subunits, was insensitive to the ATPase inhibitor, suggesting that the gamma subunit may be required for inhibition by epsilon. The partially purified delta subunit restored the capacity of ATPase deficient in delta to recombine with ATPase-depleted membranes and to reconstitute ATP-dependent transhydrogenase. Previously we reported (Biochem, Biophys. Res. Commun. 62:764 [1975]) that a fraction containing both the delta and epsilon subunits of ECF1 restored the capacity of ATPase missing delta to recombine with depleted membranes and to function as a coupling factor in oxidative phosphorylation and for the energized transhydrogenase. These reconstitution experiments using isolated subunits provide rather substantial evidence that the delta subunit is essential for attaching the ATPase to the membrane and that the epsilon subunit has a regulatory function as an inhibitor of the ATPase activity of ECF1.
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PMID:Partial purification of active delta and epsilon subunits of the membrane ATPase from escherichia coli. 12 87


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