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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Administration of chlorpromazine 10 mg/kg intraperitoneally to mice produced no alteration in cerebral adenosine triphosphate (ATP), adenosine diphosphate (ADP) or adenosine monophosphate (AMP). In these animals there was an increase in the glucose content of the supernatants of homogenates of liver and brain following acid hydrolysis.2. Chlorpromazine 40 mg/kg intraperitoneally did not affect Mg(++) activated adenosine triphosphatase (ATPase) activity in the brain.
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PMID:The effect of chlorpromazine on cerebral glucose, ATP, ADP, AMP and ATPase in the mouse. 430 Jan 44

A study was made of the enzyme content of the isolated cell walls and of a plasma-membrane preparation obtained by centrifugation after enzymic digestion of the cell walls of baker's yeast. The isolated cell walls showed no hexokinase, alkaline phosphatase, esterase or NADH oxidase activity. It was concluded that these enzymes exist only in the interior of the cell. Further, only a negligible activity of deamidase was detectable in the cell walls. Noticeable amounts of saccharase, phosphatases hydrolysing p-nitrophenyl phosphate, ATP, ADP, thiamin pyrophosphate and PP(i), with optimum activity at pH3-4, and an activity of Mg(2+)-dependent adenosine triphosphatase at neutral pH, were found in the isolated cell walls. During enzymic digestion, the other activities appearing in the cell walls were mostly released into the medium, but the bulk of the Mg(2+)-dependent adenosine triphosphatase remained in the plasma-membrane preparation. Accordingly, it may be assumed that the enzymes released into the medium during digestion are located in the cell wall outside the plasma membrane, whereas the Mg(2+)-dependent adenosine triphosphatase is an enzyme of the plasma membrane. This enzyme differs from the phosphatases with pH optima in the range pH3-4 with regard to location, pH optimum, substrate specificity and different requirement of activators.
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PMID:The enzymic composition of the isolated cell wall and plasma membrane of baker's yeast. 431 24

A nucleotide phosphohydrolase is firmly associated with a purified polyhedral cytoplasmic deoxyvirus, frog virus 3. This adenosine triphosphatase is distinguishable from known mammalian cell adenosine triphosphatases and from adenosine triphosphatase of an unrelated cytoplasmic replicating virus grown in the same host cell. The enzyme activity has a high specificity for adenosine triphosphate; the product of the reaction is adenosine diphosphate. The presence of similar activities in reovirus and poxvirus indicates that adenosine triphosphatase might have a function in the replication of these viruses.
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PMID:Proteins of polyhedal cytoplasmic deoxyvirus. II. Nucleotide phosphohydrolase activity associated with frog virus 3. 432 90

Characteristics of inorganic pyrophosphate synthesis from inorganic orthophosphate were examined in chromatophores of Rhodospirillum rubrum. The application of an ADP-glucose pyrophosphorylase-trapping system has shown in an unequivocal fashion that pyrophosphate is a product of a light-dependent reaction utilizing P(i) as the substrate. Only very limited pyrophosphate synthesis takes place in the dark. The rates of synthesis of both ATP and pyrophosphate were studied under conditions in which the membrane-bound adenosine triphosphatase and pyrophosphatase activities would normally make these substances unstable. The maximum rate of pyrophosphate synthesis was 25% of that for ATP synthesis, with maximum activation of pyrophosphate synthesis occurring at a lower light-intensity than that required for ATP synthesis. As a result, at low light-intensity the rate of pyrophosphate formation approached that of ATP. Maximal rates of synthesis of both pyrophosphate and ATP were attained only on the addition of an exogenous reducing agent. Conditions for optimum pyrophosphate synthesis required about one-half of the concentration of the reductant required for maximum ATP synthesis. Consistent with previous reports, oligomycin inhibited ATP synthesis, but had little influence on the rate of pyrophosphate synthesis. In membrane particles that retained pyrophosphatase activity but were treated to remove adenosine triphosphatase activity and the ability to photophosphorylate ADP, oligomycin stimulated light-dependent pyrophosphate synthesis by nearly 250%. The influence of Mg(2+) concentration, pH and various inhibitors and uncouplers on pyrophosphate synthesis was studied. The results are discussed with respect to the mechanism and function of electron-transport-coupled energy conservation in R. rubrum chromatophores.
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PMID:Studies on the light-dependent synthesis of inorganic pyrophosphate by Rhodospirillum rubrum chromatophores. 434 76

Treatment of an isoenzyme of potato apyrase of high adenosine triphosphatase/adenosine diphosphatase (ATPase/ADPase) ratio with iodine, N-acetylimidazole or tetranitromethane inactivates the ATPase activity of this enzyme faster than its ADPase activity. There was protection by substrates with the two last-named substances. This and the appearance of nitrotyrosine suggests the participation of tyrosyl residues in both enzymic activities of potato apyrase. The participation of thiol groups is excluded by the insensitivity of apyrase to p-chloromercuribenzoate. Also, 2-hydroxy-5-nitrobenzyl bromide or carboxymethylation produce the same rate of inactivation of ATPase and ADPase activities. Substrates protect both activities from inactivation. Hydrogen peroxide and photo-oxidation inactivate ATPase activity faster than ADPase activity. There is no protection by substrates. Analysis of pH effects on V(max.) and K(m) suggest different pK values for the amino acid residues at the ATP and ADP sites.
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PMID:Effects of protein-modifying reagents on an isoenzyme of potato apyrase. 435 57

1. Adenylyl imidodiphosphate is an inhibitor with high affinity for the soluble ATPase (adenosine triphosphatase) from mitochondria. 2. The reaction of the inhibitor with the ATPase is slow and estimates for the association and dissociation reaction rate constants are given. 3. The number of binding sites for the inhibitor appears to be doubled in the presence of 2,4-dinitrophenol. 4. Adenylyl imidodiphosphate is less effective as an inhibitor of the ATPase activity of this enzyme than of the inosine triphosphatase activity. It is also less effective on the ATPase of frozen-thawed or intact mitochondria and did not inhibit ADP-stimulated respiration by intact mitochondria.
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PMID:Inhibition of the soluble adenosine triphosphatase from mitochondria by adenylyl imidodiphosphate. 437 52

1. ATP sulphurylases were partially purified (20-40-fold) from leaf tissue of Astragalus bisulcatus, Astragalus racemosus (selenium-accumulator species) and Astragalus hamosus and Astragalus sinicus (non-accumulator species). Activity was measured by sulphate-dependent PP(i)-ATP exchange. The enzymes were separated from pyrophosphatase and adenosine triphosphatase activities. The properties of the Astragalus ATP sulphurylases were similar to the spinach enzyme. 2. The ATP sulphurylases from both selenium-accumulator and non-accumulator species catalysed selenate-dependent PP(i)-ATP exchange; selenate competed with sulphate. The ratio of V(selenate)/V(sulphate) and K(m)(selenate)/K(m)(sulphate) was approximately the same for the enzyme from each species. 3. Sulphate-dependent PP(i)-ATP exchange was inhibited by ADP, chlorate and nitrate. The kinetics of the inhibition for each enzyme were consistent with an ordered reaction mechanism, in which ATP is the first substrate to react with the enzyme and PP(i) is the first product released. 4. Synthesis of adenosine 5'-[(35)S]sulphatophosphate from [(35)S]sulphate was demonstrated by coupling the Astragalus ATP sulphurylases with Mg(2+)-dependent pyrophosphatase; the reaction was inhibited by selenate. An analogous reaction using [(75)Se]selenate as substrate could not be demonstrated.
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PMID:Comparative enzymology of the adenosine triphosphate sulphurylases from leaf tissue of selenium-accumulator and non-accumulator plants. 437 98

1. The intracellular location and maximal activities of enzymes involved in phosphoenolpyruvate synthesis have been investigated in pigeon liver. Enolase and pyruvate kinase were cytoplasmic, and the activities were 50-60 and 180-210mumoles/min./g. dry wt. at 25 degrees respectively. Phosphoenolpyruvate carboxykinase was present exclusively, and nucleoside diphosphokinase predominantly, in the mitochondria; the particles had to be disrupted to elicit maximal activities, which were 27-33 and 400-600mumoles/min./g. dry wt. at 25 degrees respectively. The activities of all four enzymes did not change significantly during 48hr. of starvation. 2. Conditions for incubation of washed isolated mitochondria were established, to give high rates of synthesis of phosphoenolpyruvate, linear with time and proportional to mitochondrial concentration. Inorganic phosphate and added adenine nucleotides were stimulatory, whereas added Mg(2+) inhibited, partly owing to activation of contaminant pyruvate kinase. Phosphoenolpyruvate formation occurred from oxaloacetate, malate, fumarate, succinate, alpha-oxoglutarate and citrate, in decreasing order of effectiveness. 3. The steady-state ATP/ADP ratio of mitochondrial suspensions was decreased in the presence of added 2.5mm-Mg(2+) (owing to stimulation of adenylate kinase and possibly of an adenosine triphosphatase), 0.5mm-Ca(2+) or 0.4mm-dinitrophenol. In each case the rate of substrate removal and oxygen uptake was increased, whereas phosphoenolpyruvate synthesis was inhibited. Citrate formation was enhanced, owing to de-inhibition of citrate synthase. These effects were not primarily related to changes in the oxaloacetate concentration. 4. Both phosphoenolpyruvate carboxykinase and nucleoside diphosphokinase were active within the atractylosidesensitive barrier to the mitochondrial metabolism of added adenine nucleotides. There was no correlation between the rate of substrate-level phosphorylation associated with the oxidation of alpha-oxoglutarate, and the synthesis of phosphoenolpyruvate. 5. The results suggest that phosphoenolpyruvate formation in pigeon-liver mitochondria is regulated partly by the phosphorylation state of the adenine and guanine nucleotides, and partly by variations in the oxaloacetate concentration, all in the mitochondrial matrix. 6. Phosphoenolpyruvate is assumed to be the metabolite transported from the mitochondria to the cytoplasm during gluconeogenesis from oxaloacetate in pigeon liver.
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PMID:The regulation of phosphoenolpyruvate synthesis in pigeon liver. 496 63

1. A radiochemical assay for glutamine synthetase has been developed in which an ATP-regenerating system is incorporated to prevent accumulation of inhibitory amounts of ADP. It is particularly suitable for assay of the enzyme in crude tissue extracts containing high adenosine triphosphatase activity. 2. A survey of the distribution of the enzyme in tissues from normal male rats showed that activity is present in liver, brain cortex, kidney cortex, spleen, testis and retina. 3. The K(m) of the enzyme for l-glutamate is approx. 1.5x10(-2)m.
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PMID:A radiochemical assay for glutamine synthetase, and activity of the enzyme in rat tissues. 547 54

1. The organic mercurial sodium mersalyl, formaldehyde, dicyclohexylcarbodiimide and tributyltin each blocked respiratory-chain-linked ATP synthesis in rat liver mitochondria. 2. Mersalyl and formaldehyde also blocked a number of other processes dependent on the entry of inorganic phosphate into mitochondria, including mitochondrial respiration and swelling stimulated by cations and phosphate, the substrate-level phosphorylation reaction of the citric acid cycle, and swelling in ammonium phosphate. 3. Dicyclohexylcarbodi-imide and tributyltin did not inhibit the entry of phosphate into mitochondria. 4. Mersalyl and formaldehyde had a relatively slight effect on succinate oxidation and swelling stimulated by cations when phosphate was replaced by acetate, on succinate oxidation stimulated by uncoupling agents, and on swelling in solutions of ammonium salts other than phosphate or arsenate. 5. Formaldehyde blocked the oxidation of NAD-linked substrates in mitochondria treated with 2,4-dinitrophenol and the ATP-dependent reduction of NAD by succinate catalysed by ox heart submitochondrial particles. Both these effects appear to be due to an inhibition by formaldehyde of the NAD-flavin region of the respiratory chain. 6. Concentrations of dicyclohexylcarbodiimide or tributyltin sufficient to abolish ADP-stimulated respiration blocked the dinitrophenol-stimulated adenosine triphosphatase activity, whereas mersalyl and formaldehyde caused only partial inhibition of ATP hydrolysis. 7. When mitochondria were incubated with dinitrophenol and ATP, less than 10% of the total inorganic phosphate liberated was recovered in the mitochondria and no swelling occurred. In the presence of mersalyl or formaldehyde at least 80% of the total inorganic phosphate liberated was retained in the mitochondria and extensive swelling was observed. This swelling was inhibited by oligomycin but not by antimycin or rotenone. 8. The addition of mersalyl to mitochondria swollen by treatment with valinomycin, K(+) and phosphate blocked the contraction induced by dinitrophenol and caused an increase in the phosphate content of the mitochondria, but had no effect on the contraction of mitochondria when phosphate was replaced by acetate. 9. It is concluded that mitochondria contain a phosphate-transporter system, which catalyses the movement of phosphate in either direction across the mitochondrial membrane, and that this system is inactivated by organic mercurials and by formaldehyde. Evidence is presented that the phosphate-transporter system is situated in the inner membrane of rat liver mitochondria and is also present in other types of mammalian mitochondria.
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PMID:Evidence of a phosphate-transporter system in the inner membrane of isolated mitochondria. 578 67


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