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 addition of 5 . 10(-5) M or less of dicyclohexylcarbodiimide to Mycoplasma mycoides var. Capri preferentially influences K+ influx rather than efflux and reduces by 30--40% the activity of the membrane-bound Mg2+- ATPase. Adding valinomycin to metabolizing cells does not markedly affect K+ distribution but induces a rapid and complete loss of intracellular K+ in non-metabolizing cells. Uncoupling agents such as dinitrophenol, carbonylcyanide p-trifluoromethoxyphenylhydrazone, dissipate the K+ concentration gradient only when combined with valinomycin. Variations in the merocyanine fluorescence intensity indicate that a transmembrane electrical potential (delta psi) is generated on cell energization. This delta psi, not affected by valinomycin or uncouplers when used alone, is collapsed by a mixture of both. No change in fluorescence intensity can be detected when glucose is added to dicyclohexylcarbodiimide treated organisms. These experiments suggest that the membrane-bound Mg-ATPase activity control K+ distribution in these organisms through the generation of a transmembrane electrical potential difference.
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PMID:Active K+ transport in Mycoplasms mycoides var. Capri. Relationships between K+ distribution, electrical potential and ATPase activity. 3 12

As different structural states of the Na+-K+-ATPase (EC 3.6.1.3) may lead to a changed reactivity to antibodies, the influence of different ligands on the reaction between highly purified membrane-bound Na+-K+-ATPase and specific antibodies was investigated. The antigen antibody reaction was registered by measuring the antibody inhibition of Na+-K+-ATPase activity. It was found that Na+ decreased and K+ increased the antibody inhibition of the Na+-K+-ATPase activity of the membrane-bound enzyme if both Mg++ and ATP were present during the antigen antibody reaction. These effects were not observed if ATP was replaced by ADP or by the ATP analog adenylyl (beta-gamma-methylene) diphosphonate. If a solubilized enzyme preparation with the same specific activity was used the effects of Na+ or K+ which were demonstrated in the membrane-bound enzyme could not be detected. The study suggests that the Na+-K+-ATPase structure is altered by Na+ and K+, provided Mg++ and specifically the nucleotide ATP are also present. These structural changes are likely to occur during Na+-K+-transport and do not seem to be necessarily linked to the Na+, K+ and Mg++ stimulated ATP splitting of the enzyme.
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PMID:Immunological characterization of Na+ and K+ mediated structural states of rat kidney Na+-k+-ATPase. 8 Mar 2

As different structural states of the (Na+-K+)-ATPase (EC 3.6.1.3) may lead to a changed reactivity to antibodies, the influence of Na+, K+, Mg++, Pi and ATP on the reaction between highly purified (Na+-K+)-ATPase and antibodies directed against the membrane-bound enzyme was measured. The antigen antibody reaction was registered by measuring the antibody inhibition of (Na+-K+)-ATPase activity. In the membrane-bound but not in the solubilized enzyme four different degrees of antibody inhibition were obtained at equilibrium of the antigen antibody reaction if different combinations of Na+, K+, Mg++ and ATP were present during the incubation with the antibodies. Corresponding to the different degrees of inhibition, different rates of enzyme inhibition were measured. (a) The smallest degree of enzyme inhibition was obtained when (i) only Mg++, (ii) Mg++ and Na+ or (iii) Mg++ and K+ were present during the antigen antibody reaction. (b) The enzyme activity was inhibited more strongly if Na+, Mg++ and ATP were present together. (c) It was inhibited even more if only (i) Na+, (ii) K+, (iii) ATP or both (iv) ATP and Na+, (v) ATP and K+, (vi) ATP and Mg++, or if (vii) no ATP and activating ions were present. (d) The highest degree of antibody inhibition was obtained if Mg++, ATP and K+ were present together. In the presence of Mg++ plus ADP and in the presence of Mg++ plus the ATP analog adenylyl (beta-gamma-methylene) diphosphonate, Na+ and K+ did not influence the degree of antibody inhibition as they did in the presence of Mg++ plus ATP. It was further found that the degree of antibody inhibition in the presence of Mg++, ATP and K+ was affected by the sequence of which K+ and ATP were added to the enzyme prior to the addition of the antibodies. It is suggested that by antibody inhibition different conformations of the (Na+-K+)-ATPase could be detected. These conformations may possibly not occur in the solubilized enzyme and therefore do not seem to be necessarily linked to the intermediary steps of the ATP hydrolysis of the enzyme. The structural changes which are induced by Na+ and K+ in the presence of Mg++ plus ATP are proposed to occur during the Na+-K+ transport.
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PMID:Conformational changes of membrane-bound (Na+-K+)-ATPase as revealed by antibody inhibition. 8 16

Plasma membranes from normal, full-term human placental trophoblast have been isolated by a new procedure. The method depends upon isopycnic zonal centrifugation using linear sucrose/Ficoll density gradients. Enrichment of plasma membrane marker enzymes with respect to trophoblast homogenate is found in two distinct peaks (designated B and D) of the fractionated effluent recovered from the rotor. Fraction B is enriched with membrane-bound alkaline phosphatase and 5'-nucleotidase, but not with (Na+, K+)-ATPase of F(-)-stimulated adenylate cyclase. It is suggested that this material is derived from the maternal-facing microvillous plasma membrane. Fraction D, enriched with (Na+, K+)-ATPase, F(-)-stimulated adenylate cyclase and, to a smaller extent, with 5'-nucleotidase and alkaline phosphatase is, by exclusion, proposed to be derived from the fetal-facing basal plasma membrane. Both plasma membrane fractions are shown to be free of appreciable contamination, using specific markers for endoplasmic reticulum, mitochondria, nuclei and lysosomes. The separation of the two membrane fractions is shown to depend both upon these membranes forming closed vesicles during homogenization and upon the buoyant densities of such vesicles differing in such a way that microvillous plasma membranes band at a lower density than basal plasma membranes. No separation of the membranes is achieved in gradients in which the vesicles are collapsed.
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PMID:Separation of the microvillous (maternal) from the basal (fetal) plasma membrane of human term placenta: methods and physiological significance of marker enzyme distribution. 9 48

Lactobacillus casei cells can accumulate folate to an intracellular concentration in excess of 500 muM and to concentration gradients (relative to the extracellular compartment) of several thousand-fold. Maximum rates of folate transport are achieved rapidly (t(1/2) < 1 min) after the addition of glucose to energy-depleted cells and occur at intracellular adenosine 5'-triphosphate concentrations above 625 muM. The rate of folate transport and the adenosine 5'-triphosphate content of cells are both extremely sensitive to arsenate and decrease in parallel with increasing concentrations of the inhibitor, indicating a requirement for phosphate-bond energy in the transport process. The energy source is not a membrane potential or a pH gradient generated via the membrane-bound adenosine triphosphatase, since dicyclohexylcarbodiimide (an adenosine triphosphatase inhibitor) and carbonyl cyanide m-chlorophenylhydrazone (a proton conductor) have little effect on the uptake process. The K(+)-ionophore, valinomycin, is an inhibitor of folate transport, but does not act via a mechanism involving dissipation of the membrane potential. This can be deduced from the facts that the inhibition by valinomycin is relatively insensitive to pH, is considerably greater in Na(+)- than in K(+)-containing buffers, and is not enhanced by the addition of proton conductors. Folate efflux is not affected by valinomycin, glucose, or various metabolic inhibitors, although a rapid release of the accumulated vitamin can be achieved by the addition of unlabeled folate together with an energy source (glucose). These results suggest that the active transport of folate into L. casei is energized by adenosine 5'-triphosphate or an equivalent energy-rich compound, and that coupling occurs not via the membrane-bound adenosine triphosphatase but by direct interaction of the energy source with a component of the transport system.
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PMID:Coupling of energy to folate transport in Lactobacillus casei. 11 Jul 91

Active transport of proline remained unaffected in phospholipase A-treated electron transport particles from Mycobacterium phlei. However, the steady state level of proline was reduced 50 to 60% in phospholipase A-treated depleted electron transport particles that were devoid of membrane-bound coupling factor-latent ATPase activity. The decrease in the uptake of proline in the phospholipase A-treated depleted electron transport particles was not due to a change in the apparent K-m for proline, but it was related to the amount of phospholipid cleaved from the membranes. Restoration in the level of proline transport in phospholipase A-treated depleted electron transport particles was achieved by reconstituting these vesicles with diphosphatidylglycerol and phosphatidylethanolamine liposomes. Diphosphatidylglycerol was found to be most effective in the restoration of proline uptake. In contrast to the effect of phospholipase A treatment on proline transport, similar treatement of the electron transport particles or depleted electron transport particles failed to inhibit the active transport of either glutamine or glutamic acid. Studies with phospholipase A-treated membrane vesicles confirmed earlier findings that a proton gradient is not required for active transport of amino acids.
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PMID:Effect of phospholipase A on active transport of amino acids with membrane vesicles of Mycobacterium phlei. 12 19

Cytochalasin A at 10-20 mug/ml inhibits growth and sugar uptake by Saccharomyces strain 1016. The effects of cytochalasin A in intact cells were completely prevented when 1 mM cysteine or dithiothreitol was added along with cytochalasin A, but were not eliminated by thiols added after inhibition had occurred. Purified yeast hexokinase, glucose-6-P dehydrogenase, phosphofructokinase and aldolase were not sensitive to cytochalasin A (20 mug/ml). Glyceraldehyde-3-P dehydrogenase was strongly inhibited by cytochalasin A (5 mug/ml); activity was promptly restored by thiols. Anaerobic glycolysis was inhibited by cytochalasin A or by iodoacetate; unlike iodoacetate, cytochalasin A did not cause accumulation of sugar phosphates. In contrast, cytochalasin A, but not iodoacetate, inhibited isolated membrane-bound ATPases. Cytochalasin A is a sulfhydryl-reactive agent and has membrane-related effects (adenosine triphosphatase) which may well be the basis of its interference with energy-dependent uptake of solutes.
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PMID:Action of cytochalasin A, a sulfhydryl-reactive agent, on sugar metabolism and membrane-bound adenosine triphosphatase of yeast. 12 88

The mechanism of action of the cytotoxic protein P6 isolated from cobra venom (Naja naja) which shows preferential cytotoxicity particularly to Yoshida sarcoma cells has been studied by its effects on the membrane-bound enzyme (Na-++K-+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) of a variety of cell systems. Evidence obtained with Yoshida sarcoma cells, dog and human erythrocytes and three tissue culture cell lines KB (human oral carcinoma), Hela (human cervix carcinoma) and L-132 (human lung embryonic) shows that inhibition of (Na-++K-+)-ATPase by the P6 protein can be correlated with its lytic activity. (Na-++k-+)-ATPase of Yoshida sarcoma membrane fragments inactivated by P6 protein could be reconstituted by the addition of phosphatidylserine and phosphatidic acid. It is conceivable that lysis of cells by the P6 protein may be due to an imbalance of K-+ and Na-+ in the cell which leads to swelling and disintegration of the membrane structure. Observations indicate that the P6 protein combines with membrane constituents of susceptible cells. The overall evidence suggests that both the specificity of its protein structure and the highly basic nature of the P6 protein are factors which enable it to compete with the lipid moiety maintaining the (Na-++k-+)-ATPase of the susceptible cells in proper conformation for activity.
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PMID:Inactivation of (Na-++K-+)-stimulated ATPase by a cytotoxic protein from cobra venom in relation to its lytic effects on cells. 12 1

The hormonal responsiveness of plasma membrane-bound enzymes (Na-+-K-+)-ATPase and adenylate cyclase has been investigated in normal and regenerating rat liver. (Na-+-K-+)-ATPase basal activity is not affected by surgery and only slightly affected by partial hepatectomy; its response to epinephrine and cyclic AMP is decreased only 15 h after hepatectomy. Adenylate cyclase activity of plasma membranes from untreated animals is stimulated by parathyroid hormone and thyroxine; partial hepatectomy increased basal activity as well as the stimulation exerted by the aforementioned hormones, when glucagon and epinephrine sensitivity is essentially unaltered.
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PMID:Hormone responsiveness of plasma membrane-bound enzymes in normal and regenerating rat liver. 12 2

Ouabain, which inhibits specifically membrane-bound ATPase activity, also inhibits the establishment of the antiviral state induced by interferon. Once the antiviral state is established, ouabain is ineffective. This inhibitory effect is reversed by adding Na/K ions to the cells. On the contrary, interferon production is unaffected by the same concentrations of ouabain. It is of interest that in such interferon-yielding cells, ouabain decreases the antiviral state.
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PMID:Different effect of ouabain on the interferon production and action. 12 71


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