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)

1. 30mmum-4,5,6,7-Tetrachloro-2-trifluoromethylbenzimidazole (TTFB) uncouples respiratory-chain phosphorylation. The respiration rate of uncoupled mitochondria is significantly greater than the state 3 rate. Neither added orthophosphate nor ATP is required to sustain this rate. The oligomycin- and octylguanidine-induced inhibitions of respiration are relieved by uncoupling concentrations of TTFB. 2. Uncoupling concentrations of TTFB elicit a high adenosinetriphosphatase activity and inhibit the ATP-dependent succinate-linked reduction of NAD catalysed by submitochondrial particles from ox-heart mitochondria. 3. The action of TTFB is similar to that of 2,4-dinitrophenol. Evidence is presented which shows that it is the anionic forms of benzimidazoles and imidazoles, having the negative charge localized on the ring nitrogen atom, which are the effective uncoupling agents.
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PMID:The uncoupling of respiratory-chain phosphorylation by 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole. 422 43

Transient kinetic studies of Mg(2+)-dependent heavy-meromyosin ATPase (adenosine triphosphatase) were done by monitoring the release of both ADP and P(i) into the reaction medium by using linked assay systems. The release of P(i) was monitored by its quantitative transfer to ADP, with concomitant reduction of NAD(+) in the presence of d-glyceraldehyde 3-phosphate, d-glyceraldehyde 3-phosphate dehydrogenase and phosphoglycerate kinase. The dissociation rates of the products, ADP and P(i), from heavy meromyosin were shown to be faster than the rate-controlling process, which occurs after the initial bond cleavage of ATP. The chromophoric ATP analogue, 6-mercapto-9-beta-d-ribofuranosylpurine 5'-triphosphate (thioATP) was used as a substrate and spectral changes associated with a single turnover of heavy meromyosin could be assigned to elementary processes of the mechanism. It was shown that the dissociation rate of thioADP was not the rate-controlling process of the thioATPase, whose catalytic-centre activity was 7.6 times that of the ATPase at pH8. The dissociation rate of ADP from heavy meromyosin was measured by using thioATP as displacing agent and was found to be 2.3s(-1), which is about 50 times the catalytic-centre activity of the ATPase at pH8. Transient kinetic studies with chromophoric adenosine phosphate analogues have general application for kinases and ATPases both in characterizing the chemical states of the intermediates and in delineating the elementary processes of the enzyme mechanism.
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PMID:Elementary processes of the magnesium ion-dependent adenosine triphosphatase activity of heavy meromyosin. A transient kinetic approach to the study of kinases and adenosine triphosphatases and a colorimetric inorganic phosphate assay in situ. 426 38

1. The effects of dicyclohexylcarbodi-imide, oligomycin A and aurovertin on enzyme systems related to respiratory-chain phosphorylation were compared. Dicyclohexylcarbodi-imide and oligomycin A have very similar functional effects, giving 50% inhibition of ATP-utilizing and ATP-generating systems at concentrations below 0.8nmole/mg. of submitochondrial-particle protein. Aurovertin is a more potent inhibitor of ATP synthesis, giving 50% inhibition at 0.2nmole/mg. of protein. However, aurovertin is a less potent inhibitor of ATP-utilizing systems: the ATP-driven energy-linked nicotinamide nucleotide transhydrogenase is 50% inhibited at 3.0nmoles/mg. of protein and the ATP-driven reduction of NAD(+) by succinate is 50% inhibited at 0.95nmole/mg. of protein. 2. With EDTA-particles (prepared by subjecting mitochondria to ultrasonic radiation at pH9 in the presence of 2mm-EDTA) the maximum stimulation of the ATP-driven partial reactions is effected by similar concentrations of oligomycin A and dicylcohexylcarbodi-imide, but the latter is less effective. The stimulatory effects of suboptimum concentrations of dicyclohexylcarbodi-imide and oligomycin A are additive. Aurovertin does not stimulate these reactions or interfere with the stimulation by the other inhibitors. 3. Dicyclohexylcarbodi-imide and oligomycin A stimulate the aerobic energy-linked nicotinamide nucleotide transhydrogenase of EDTA-particles, but the optimum concentration is higher than that required for the ATP-driven partial reactions. Aurovertin has no effect on this reaction. 4. The site of action of dicyclohexylcarbodi-imide is in CF(0), the mitochondrial fraction that confers oligomycin sensitivity on F(1) mitochondrial adenosine triphosphatase.
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PMID:A comparison of the effects of NN'-dicyclohexylcarbodi-imide, oligomycin A and aurovertin on enrgy-linked reactions in mitochondria and submitochondrial particles. 429 26

Exposure of red cells to fluoride produces a variety of metabolic alterations, most of which are based upon the secondary effects of enolase inhibition, which reduces pyruvate synthesis and interferes with the regeneration of diphosphopyridine nucleotide (NAD). Adenosine triphosphate (ATP) is consumed in the hexokinase and phosphofructokinase reactions but is not regenerated since the deficiency of NAD limits glyceraldehyde phosphate dehydrogenase. ATP depletion in the presence of fluoride and calcium induces a massive loss of cations and water. Of the other known sites of ATP utilization, membrane-bound ATPase is inhibited by fluoride, but the incorporation of fatty acids into membrane phospholipids is unaffected until ATP is depleted. The addition of methylene blue to fluoride-treated red cells regenerates NAD, permitting triose oxidation and the generation of 3-phosphoglycerate and 2,3-diphosphoglycerate. Enolase inhibition is then partially overcome by mass action, and sufficient glycolysis proceeds to maintain the concentration of ATP. This in turn prevents the massive cation and water loss, and permits membrane phospholipid renewal to proceed. Membrane ATPase activity is not restored by the oxidant so that normal cation leakage remains unopposed by cation pumping in red cells exposed to the combination of fluoride and methylene blue.
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PMID:Energy metabolism in human erythrocytes. I. Effects of sodium fluoride. 432 3

The rate coefficient for (22)Na release from previously labeled human erythrocytes was determined in the presence of 0.1-10 mM sodium fluoride (F). The oxidized nicotinamide adenine dinucleotide (NAD(+)) level at the end of 2 hr of incubation in tris(hydroxymethyl)aminomethane (Tris)-Ringer medium was also measured. Both parameters decreased proportionately as F concentration was raised. Both F-induced changes were immediate and were reversed by 10 mM pyruvate. The decrease in NAD(+) concentration following enolase inhibition by F is attributed to a diminished rate of formation in the reaction catalyzed by lactic dehydrogenase (LDH) with undiminished continued utilization in the reaction catalyzed by glyceraldehyde-3-phosphate dehydrogenase (GAPDH). It is postulated that the NAD(+) lowering limited the GAPDH step, resulting in proportionate decreases in the rates of phosphoglycerate kinase (PGK) and Na,K-dependent adenosine triphosphatase (Na,K-ATPase), a reaction sequence thought to link glycolysis with active Na extrusion. Adding pyruvate with F increased NAD(+) production at the LDH step, thus reactivating GAPDH, PGK, and Na,K-ATPase and leading to the observed restoration of (22)Na release. The results suggest, therefore, that F inhibits active Na transport in intact human erythrocytes indirectly through a lowering of NAD(+), although, direct inhibition of the Na,K-ATPase by F may possibly occur simultaneously.
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PMID:The role of oxidized nicotinamide adenine dinucleotide in fluoride inhibition of active sodium transport in human erythrocytes. 434 51

1. Induction of the formation of lipid peroxide in suspensions of liver microsomal preparations by incubation with ascorbate or NADPH, or by treatment with ionizing radiation, leads to a marked decrease of the activity of glucose 6-phosphatase. 2. The effect of peroxidation can be imitated by treating microsomal suspensions with detergents such as deoxycholate or with phospholipases. 3. The substrate, glucose 6-phosphate, protects the glucose 6-phosphatase activity of microsomal preparations against peroxidation or detergents. 4. The loss of glucose 6-phosphatase activity is not due to the formation of hydroperoxide or formation of malonaldehyde or other breakdown products of peroxidation, all of which are not toxic to the enzyme. 5. All experiments lead to the conclusion that the loss of activity of glucose 6-phosphatase resulting from peroxidation is a consequence of loss of membrane structure essential for the activity of the enzyme. 6. In addition to glucose 6-phosphatase, oxidative demethylation of aminopyrine or p-chloro-N-methylaniline, hydroxylation of aniline, NADPH oxidation and menadione-dependent NADPH oxidation are also strongly inhibited by peroxidation. However, another group of enzymes separated with the microsomal fraction, including NAD(+)/NADP(+) glycohydrolase, adenosine triphosphatase, esterase and NADH-cytochrome c reductase are not inactivated by peroxidation. This group is not readily inactivated by treatment with detergents. 7. Lipid peroxidation, by controlling membrane integrity, may exert a regulating effect on the oxidative metabolism and carbohydrate metabolism of the endoplasmic reticulum in vivo.
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PMID:Effects of lipid peroxidation on membrane-bound enzymes of the endoplasmic reticulum. 439 3

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

In heart slices of guinea pig, ouabain (10(-5) M) causes not only an inhibition of the Na+,-K+-ATPase but also damage of the cell membrane. This leads to an efflux and a degradation of the cellular NADH and NAD. By addition of these constituents to the incubation medium an increasing inhibition of the tissue respiration, caused by ouabain, is prevented.
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PMID:[Impairing effect of ouabain on heart muscle slices of guinea pigs]. 609 28

A histochemical study of the metabolism of rat renal arteries and arterioles. Rat renal arteries and arterioles were examined histochemically to determine their metabolic profiles. Succinate, malate and NAD-isocitrate dehydrogenase, cytochrome oxidase and ubiquinone were assessed to determine aerobic metabolism. Glucose-6-phosphate dehydrogenase and DPN diaphorase were evaluated to determine hexose-monophosphate-shunt activity. Anaerobic metabolism was evaluated via lactate dehydrogenase, and the substrate, glycogen. Gomori's lipase, beta-hydroxybutyrate dehydrogenase and amounts of neutral fat and free fatty acids were assessed as indicators of lipid utilization. Myosin ATPase activity was evaluated as an index of ATP utilization for contraction. Deoxyribonucleic and ribonucleic acids were appraised as indicators of protein synthesis. In general, the oxidative enzymes and myosin ATPase demonstrate considerable activity in renal arteries and arterioles which suggests aerobic metabolism and ATP usage. Renal arteries and arterioles also appear capable of anaerobic metabolism as indicated by strong lactate dehydrogenase reactivity and by the presence of slight to moderate quantities of glycogen, while high levels of glucose-6-phosphate dehydrogenase and moderate amounts of deoxyribonucleic acid suggest a potential for beta-hydroxybutyrate dehydrogenase, minimal lipase activity, and the absence of fatty acids with substantial amounts of neutral fat, indicate limited lipid catabolism.
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PMID:A histochemical study of the metabolism of rat renal arteries and arterioles. 620 11

The effect of lonidamine, an antispermatogenic and antitumor drug, on the oxygen consumption, ATPase activity, and redox state of the electron carriers of Ehrlich ascites tumor mitochondria has been studied. Lonidamine inhibits ADP- and uncoupler-stimulated respiration on various NAD- and FAD-linked substrates, but does not affect state 4 respiration. Experiments to determine its site of action showed that lonidamine does not significantly inhibit electron flow through cytochrome oxidase. Electron flow through site 2, the ubiquinone-cytochrome b-cytochrome c1 complex, also was unaffected by lonidamine, which failed to inhibit the oxidation of duroquinol. Moreover, inhibition of electron flow through site 2 was also excluded because of the inability of the N,N,N',N'-tetramethyl-p-phenylenediamine bypass to relieve the lonidamine inhibition of the oxidation of pyruvate + malate. The F0F1ATPase activity and vectorial H+ ejection are also unaffected by lonidamine. The inhibition of succinate oxidation by lonidamine was found to take place at a point between succinate and iron-sulfur center S3. Spectroscopic experiments demonstrated that lonidamine inhibits the reduction of mitochondrial NAD+ by pyruvate + malate and other NAD-linked substrates in the transition from state 1 to state 4. However, lonidamine does not inhibit reduction of added NAD+ by submitochondrial vesicles or by soluble purified NAD-linked dehydrogenases. These observations, together with other evidence, suggest that electron transport in tumor mitochondria is inhibited by lonidamine at the dehydrogenase-coenzyme level, particularly when the electron carriers are in a relatively oxidized state and/or when the inner membrane-matrix compartment is in the condensed state. The action of lonidamine in several respects resembles the selective inhibition of electron transport in tumor cells produced by cytotoxic macrophages (D. L. Granger and A. L. Lehninger (1982) J. Cell Biol. 95, 527).
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PMID:Action of the antitumor and antispermatogenic agent lonidamine on electron transport in Ehrlich ascites tumor mitochondria. 622 86


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