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)

Light-induced ATP synthesis was studied in intact cells and chromatophores of Erythrobacter sp. strain OCh114. ATP synthesis was measured by both the pH method and the luciferin-luciferase luminescence method. The rate of ATP synthesis was moderate (a typical value of 0.65 mol of ATP per mol of bacteriochlorophyll per min), and synthesis was inhibited by antimycin A. ATP was synthesized under illumination only under aerobic conditions and not under anaerobic conditions. This characteristic was similar to that of other light-induced energy transduction processes in this bacterial species, such as oxidation of reaction center, oxidation of cytochrome c551, and translocation of H+, which were not observed under anaerobic conditions. This phenomenon was reconciled with the fact that the Erythrobacter sp. could not grow anaerobically even in the light. The characteristics of oxidative phosphorylation and ATP hydrolysis were also investigated. The respiratory ratio of chromatophores was 2.3. Typical rates of oxidative phosphorylation by NADH and by succinate were 2.9 mol of ATP per mol of bacteriochlorophyll per min (P/O = 0.22) and 1.1 mol of ATP per mol of bacteriochlorophyll per min (P/O = 0.19), respectively. A typical rate of ATP hydrolysis was 0.25 mol of ATP per mol of bacteriochlorophyll per min in chromatophores. ATPase and adenylate kinase are also involved in the metabolism of adenine nucleotides in this bacterium.
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PMID:Photophosphorylation and oxidative phosphorylation in intact cells and chromatophores of an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114. 378 35

Mitochondria from the muscle of the parasitic nematode Ascaris lumbricoides var. suum function anaerobically in electron transport-associated phosphorylations under physiological conditions. These helminth organelles have been fractionated into inner and outer membrane, matrix, and intermembrane space fractions. The distributions of enzyme systems were determined and compared with corresponding distributions reported in mammalian mitochondria. Succinate and pyruvate dehydrogenases as well as NADH oxidase, Mg(++)-dependent ATPase, adenylate kinase, citrate synthase, and cytochrome c reductases were determined to be distributed as in mammalian mitochondria. In contrast with the mammalian systems, fumarase and NAD-linked "malic" enzyme were isolated primarily from the intermembrane space fraction of the worm mitochondria. These enzymes are required for the anaerobic energy-generating system in Ascaris and would be expected to give rise to NADH in the intermembrane space. The need for and possible mechanism of a proton translocation system to obtain energy generation is suggested.
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PMID:Enzyme localization in the anaerobic mitochondria of Ascaris lumbricoides. 415 73

1. A microsomal fraction from ox cerebral cortex catalysed [(14)C]ADP-ATP exchange at a speed similar to that at which it liberated P(i) from ATP in the presence of Na(+), K(+) and Mg(2+). 2. Repeated washing the fraction with MgATP solutions solubilized most of the exchange activity and left the adenosine triphosphatase insoluble and little changed in activity. The exchange activity was accompanied by negligible adenosine-triphosphatase activity and was enriched by precipitation at chosen pH and by DEAE-Sephadex. At no stage was its activity affected by Na(+), K(+) or ouabain. 3. The washed microsomal fraction was exposed to a variety of reagents; a sodium iodide-cysteine treatment increased both adenosine-triphosphatase and exchange activities, as also did a synthetic zeolite. Preparations were obtained with exchange activities less than 3% of their Na(+)-plus-K(+)-stimulated adenosine-triphosphatase activity. Some contribution to the residual exchange activity was made by an adenylate kinase. 4. Thus over 95% of the microsomal ADP-ATP-exchange activity does not take part in the Na(+)-plus-K(+)-stimulated adenosine-triphosphatase reaction. Participation of some of the residual 3% of the ADP-ATP-exchange activity has not been excluded, but there appears no firm evidence for its participation in the adenosine triphosphatase; the bearing of this conclusion on mechanisms proposed for the Na(+)-plus-K(+)-stimulated adenosine triphosphatase is indicated.
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PMID:Separation of adenosine diphosphate--adenosine triphosphate-exchange activity from the cerebral microsomal sodium-plus-potassium ion-stimulated adenosine triphosphatase. 422 77

Squid giant axons were internally dialyzed by a technique previously described. In an axon exposed to cyanide seawater for 1 hr and dialyzed with an ATP-free medium, the Na efflux had a mean value of 1.3 pmole/cm(2)sec when [Na](i) was 88 mM, in quantitative agreement with flux ratio calculations for a purely passive Na movement. When ATP at a concentration of 5-10 mM was supplied to the axoplasm by dialysis, Na efflux rose almost 30-fold, while if phosphoarginine, 10 mM, was supplied instead of ATP, the Na efflux rose only about 15-fold. The substitution of Li for Na in the seawater outside did not affect the Na efflux from an axon supplied with ATP, while a change to K-free Na seawater reduced the Na efflux to about one-half. When special means were used to free an axon of virtually all ADP, the response of the Na efflux to dialysis with phosphoarginine (PA) at 10 mM was very small (an increment of ca. 3 pmole/cm(2)sec) and it can be concluded that more than 96% of the Na efflux from an axon is fueled by ATP rather than PA. Measurements of [ATP] in the fluid flowing out of the dialysis tube when the [ATP] supplied was 5 mM made it possible to have a continuous measurement of ATP consumption by the axon. This averaged 43 pmole/cm(2)sec. The ATP content of axons was also measured and averaged 4.4 mM. Estimates were made of the activities of the following enzymes in axoplasm: ATPase, adenylate kinase, and arginine phosphokinase. Values are scaled to 13 degrees C.
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PMID:Some factors influencing sodium extrusion by internally dialyzed squid axons. 422 31

Treatment of the inner membrane matrix fraction of rat liver mitochondria with the nonionic detergent Lubrol WX solubilized about 70% of the total protein and 90% or more of the following matrix activities: malate dehydrogenase, glutamate dehydrogenase, and isocitrate dehydrogenase (NADP). The Lubrol-insoluble fraction was enriched in cytochromes, phospholipids, and a Mg(++)-stimulated ATPase activity. Less than 2% of the total mitochondrial activity of monoamine oxidase, an outer membrane marker, or adenylate kinase, an intracristal space marker could be detected in this inner membrane fraction. Electron micrographs of negatively stained preparations showed vesicles (</=0.4 micro diameter) literally saturated on the periphery with the 90 A ATPase particles. These inner membrane vesicles, which appeared for the most part to be inverted with respect to the normal inner membrane configuration in intact mitochondria, retained the succinicoxidase portion of the electron-transport chain, an intact phosphorylation site II with a high affinity for ADP, and the capacity to accumulate Ca(++). A number of biochemical properties characteristic of intact mitochondria and the inner membrane matrix fraction, however, were either absent or markedly deficient in the inner membrane vesicles. These included stimulation of respiration by either ADP or 2,4-dinitrophenol, oligomycin-sensitive ADP-ATP exchange activity, atractyloside sensitivity of adenine nucleotide requiring reactions, and a stimulation of the Mg(++)-ATPase by 2,4-dinitrophenol.
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PMID:Biochemical and ultrastructural properties of a mitochondrial inner membrane fraction deficient in outer membrane and matrix activities. 425 78

1. Resealed red cell ghosts containing a variety of nucleoside triphosphates, or a mixture of tri- and diphosphates, were allowed to lose (24)Na into a 10 mM-K medium or a K-free high-Na medium in the presence and absence of ouabain.2. Only ATP supported a ouabain-sensitive Na:K exchange in the 10 mM-K medium, or a ouabain-sensitive Na:Na exchange in the K-free medium.3. Because of ATPase and adenylate kinase activity, it is difficult to control the levels of ATP and ADP inside resealed red cell ghosts. Some control was achieved by incorporating into the ghosts an ATP regenerating system consisting of creatine phosphate and creatine kinase.4. Measurements of (24)Na efflux from ghosts prepared in this way showed that ADP is required for the ouabain-sensitive exchange of Na that occurs in K-free high-Na media, but not for the normal exchange of Na for K that occurs in K-containing media.5. The significance of these findings is discussed.
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PMID:Nucleotide requirements for sodium-sodium exchange catalysed by the sodium pump in human red cells. 425 32

Two enzymes of polyisoprenoid synthesis, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase (mevalonate:NADP oxidoreductase [acylating CoA], EC 1.1.1.34) and mevalonate kinase (ATP:mevalonate 5-phosphotransferase, EC 2.7.1.36), are present in the microsomal and soluble fractions of Neurospora crassa, respectively. HMG CoA reductase specifically uses NADPH as reductant and has a K(m) for dl-HMG CoA of 30 micro M. The activities of HMG CoA reductase and mevalonate kinase are low in conidia and increase threefold during the first 12 hr of stationary growth. Maximum specific activities of both enzymes occur when aerial hyphae and conidia first appear (2 days), but total activities peak later (3-4 days). Addition to the growth media of ergosterol or beta-carotene, alone or in combination, does not affect the specific or total activity of either enzyme. The mevalonate kinase of N. crassa, purified 200-fold to a specific activity of 5 micro moles/min/mg, is free from HMG CoA reductase, phosphomevalonate kinase, ATPase, adenylate kinase, and NADH oxidase activities. Mevalonate kinase specifically requires ATP as cosubstrate and exhibits a marked preference for Mg(2+) over Mn(2+), especially at high ratios of divalent metal ion to ATP. Kinase activity is inhibited by p-hydroxymercuribenzoate, and this inhibition is partially prevented by mevalonate or MgATP. Optimum activity occurs at pH 8.0-8.5 and at about 55 degrees C. The Neurospora kinase, like that of hog liver, has a sequential mechanism for substrate addition. The Michaelis constants obtained were 2.8 mM for dl-mevalonate and 1.8 mM for MgATP(-2). Geranyl pyrophosphate is an inhibitor competitive with MgATP (K(i) = 0.11 mM).
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PMID:3-Hydroxy-3-methylglutaryl CoA reductase and mevalonate kinase of Neurospora crassa. 436 66

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

Adenosine was converted into the arsonomethyl analogue of AMP. The reactions used provide a general route for converting an alcohol, R-CH2-OH, into the arsonomethyl analogue, R-CH2-CH2-AsO3H2, of its phosphate, R-CH2-O-PO3H2. The analogue of AMP proves to be a substrate for rabbit adenylate kinase, which shows a limiting velocity with it of 1/17 that with AMP, a Michaelis constant raised 70-fold to about 10 mM, and hence a specificity constant lowered about 1200-fold. The product of transfer of a phospho group from ATP to the analogue is, like all anhydrides of arsonic acids, unstable to hydrolysis, and so breaks down to yield orthophosphate and regenerate the analogue. Hence adenylate kinase is converted into an ATPase by the presence of the analogue.
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PMID:The arsonomethyl analogue of adenosine 5'-phosphate. An uncoupler of adenylate kinase. 608 48

Gastric vesicles enriched in (H+,K+)-ATPase were prepared from hog fundic mucosa and studied for their ability to transport K+ using 86Rb+ as tracer. In the absence of ATP, the vesicles elicited a rapid uptake of 86Rb+ (t 1/2 = 45 +/- 9 s at 30 degrees C) which accounted for both transport and binding. Transport was osmotically sensitive and was the fastest phase. It was not limited by anion permeability (C1- was equivalent to SO2-4) but rather by availability of either H+ or K+ as intravesicular countercation suggesting a Rb+-K+ or a Rb+-H+ exchange. Selectivity was K+ greater than Rb+ greater than Cs+ much greater than Na+,Li+. The capacity of vesicles which catalyzed the fast transport of K+ was 83 +/- 4% of maximal vesicular capacity of the fraction. Addition of ATP decreased both rate and extent of 86Rb+ uptake (by 62 and 43%, respectively with 1 mM ATP) with an apparent Ki of 30 microM. Such an effect was not seen on 22Na+ transport. ATP inhibition of transport did not require the presence of Mg2+, and inhibition was also produced by ADP even in the presence of myokinase inhibitor. On the other hand, 86Rb+ uptake was as strongly inhibited by 200 microM vanadate in the presence of Mg2+. Efflux studies suggested that ATP inhibition was originally due to a decrease of vesicular influx with little or no modification of efflux. Since ATP, ADP, and vanadate are known modulators of the (H+,K+)-ATPase, we propose that, in the absence of ATP, (H+,K+)-ATPase passively exchanges K+ for K+ or H+ and that ATP, ADP, and vanadate regulate this exchange.
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PMID:Passive transport of Rb+ by hog gastric (H+,K+)-ATPase. 609 Apr 49


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