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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 effect of heliomycin and known uncouplers of oxidative phosphorylation on respiration and oxidative phosphorylation was studied comparatively. Heliomycin, as well as 2,4-dinitrophenol, valinomycin and gramicidin S inhibited the mitochondrial synthesis of ATP. This process was inhibited completely by heliomycin at a concentration of 1.5 x 10(-5) M. The synthesis of inorganic pyrophosphate, the other macroergic compound, was also inhibited by heliomycin, ATPase and pyrophosphatase of uncoupled mitochondria being not inhibited by the antibiotic. Like 2,4-dinitrophenol, heliomycin stimulated the synthesis of ATPase and respiration in intact mitochondria. Probably, heliomycin inhibited the synthesis of ATP and pyrophosphate by uncoupling the processes of respiration and oxidative phosphorylation. It was shown earlier that heliomycin, a specific inhibitor of bacterial RNA synthesis, also affected energy metabolism of bacterial cells by inhibiting the synthesis of ATP and active transport.
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PMID:[Effect of heliomycin on the respiration and oxidative phosphorylation of the liver mitochondria of the rat]. 630 59

The subcellular distribution of the Na+/H+ antiporter in renal proximal tubule cells was studied with differential and density gradient centrifugation. Enzyme markers for basolateral membranes [Na+/K+)-ATPase), brush border membranes (maltase), and a variety of intracellular organelles (NADPH cytochrome c reductase, thiamine pyrophosphatase, acid phosphatase, and succinate cytochrome c reductase) were simultaneously assayed in sucrose density gradients. Basolateral membranes (median rho = 1.150) were well separated from brush border membranes (median rho = 1.165) by this technique. Markers for other cellular organelles had intermediate or bimodal distributions. To determine the cellular location of the Na+/H+ antiporter, Na+-dependent collapse of preformed pH gradients was assayed in the sucrose density gradient fractions using acridine orange. Na+/H+ antiporter activity paralleled the distribution of the brush border membrane fractions; activity in the peak basolateral membrane fraction was less than 5% of that in the peak brush border fraction. To determine whether antiporter activity was potentially detectable in all cell fractions, nigericin was added to each fraction and K+/H+ exchange was assayed with acridine orange. Activity was present in all sucrose density gradient fractions. In addition, there was no alteration in Na+/H+ exchange activity measured in brush border membranes after mixing with cell sol or basolateral membranes, showing that neither inhibitors nor activators of the Na+/H+ antiporter were present in any of the cell fractions. These controls confirmed the finding that Na+/H+ antiporter activity was absent from basolateral membranes. The presence of the Na+/H+ antiporter in brush border membranes and its absence from basolateral membranes is consistent with its playing an important role in the vectorial transport of H+ from blood to tubular lumen in the renal proximal tubule.
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PMID:Asymmetric distribution of the Na+/H+ antiporter in the renal proximal tubule epithelial cell. 631 99

Although there is some evidence that extrachoroidal sites for the production of cerebrospinal fluid (CSF) are important, the choroid plexuses in the ventricles contribute the major part of CSF formation. The exact mechanism for CSF production is not fully understood. In order to study this mechanism from the enzyme histochemical standpoint, the previously reported studies are reviewed, in addition to the authors' own electron microscopic enzyme histochemical observations on this tissue. The ultrastructure and enzyme biochemistry of choroid plexus epithelial cells are considered, together with the histochemistry of the following enzymes: alkaline and acid phosphatase, Mg2+-ATPase, Na+, K+-ATPase, glucose-6-phosphatase, thiamine pyrophosphatase, adenylate cyclase, carbonic anhydrase, oxidoreductase, esterase, several hydrolases, and other enzymes. Finally, CSF formation and active transport in the choroid plexus epithelial cells are discussed, mainly in terms of the results of our enzyme cytochemical observations on Na+, K+-ATPase and carbonic anhydrase in this tissue.
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PMID:The enzyme histochemistry of the choroid plexus. 683 Nov 99

To show adenylate cyclase (AC) activity in rat calvaria, it is necessary first to decalcify the specimen. In hard tissues, several enzymes (adenosine triphosphatase (ATPase), alkaline phosphatase (APase), adenylate cyclase (AC) and perhaps pyrophosphatase (PPiase) are able to degrade adenosine triphosphate (ATP). The presence of sodium fluoride (NaF) in the incubation medium reduces the quantity of precipitate formed, compared to that observed using a NaF-free incubation medium. Levamisole, used under the same conditions, gives similar results. Possibly NaF inhibits pyrophosphohydrolase and/or phosphatases which mask the AC activity. Adenylylimidophosphate (AMP-PNP), which is a specific AC substrate, confirms the results obtained with ATP. AC activity is demonstrated cytochemically in the osteoblast and preosteoblast membranes, at the junction between two osteoblasts and along the cytoplasmic processes of the osteoblast which penetrate into the osteoid matrix. The osteocytes never show a precipitate, except those which present some osteoblastic features and then only on the membrane facing the osteogenic layer. An intracellular reaction is also evident and is discussed. Parathyroid hormone (PTH) does not reveal new sites of AC activity but increases the quantity of precipitate observed.
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PMID:An attempt at localizing adenylate cyclase in rat calvaria. Influence of sodium fluoride and parathyroid hormone. 700 93

The effect of concanavalin A on biosynthesis of nucleic acids, proteins, structural polysaccharides and glycoproteins of the yeast cell membrane and of enzymes having different localization in the cell as well as on other processes occurring in spheroplasts of the yeasts Saccharomyces cerevisiae IBPhM-350 and CCY 21-4-13 were studied. In both yeast strains lectin strongly inhibited total protein synthesis and produced a weaker inhibiting effect on DNA and RNA synthesis. This was accompanied by a decrease of the activity of the majority of already known enzymes (acid phosphatase, invertase, alpha-glucosidase, polyphosphatase, pyrophosphatase, ATPase) and glucose consumption. In addition concanavalin A inhibited the synthesis of structural components of the yeast cell membrane, i.e. mannane and glucane. The data obtained suggest that lectin (50 microgram/ml or higher) has a toxic effect on yeast spheroplasts (or protoplasts).
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PMID:[Inhibiting effect of concanavalin A on certain biosynthetic processes in spheroplasts of the yeast Saccharomyces cerevisiae]. 705 45

The effect of stannous chloride on bone metabolism was examined in weanling male rats given oral dose of 1.0 mg Sn/kg at 12-h intervals for 28 days. Tin administration produced progressive increase in tin content of the femoral diaphysis and epiphysis. Calcium content in the femoral epiphysis but not diaphysis was significantly decreased by tin administration for 28 days, while inorganic phosphorus contents in the femoral diaphysis and epiphysis were not changed significantly. Acid and alkaline phosphatase activities in the femoral diaphysis and epiphysis were markedly reduced by tin administration for 3 days, and significant decreases in the femoral epiphysis were also observed at 28 days. Meanwhile, ATPase and pyrophosphatase activities in the femoral diaphysis and epiphysis were not altered significantly by tin administration. From the present study, of mineral composition and its related enzyme activity, the decreases of acid and alkaline phosphatase activities in the femoral epiphysis were regarded as the biochemical manifestation of the toxic action of inorganic tin.
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PMID:Changes in mineral composition and its related enzyme activity in the femur of rats orally administered stannous chloride. 732 88

The present study was undertaken to determine whether vacuolar H(+)-pyrophosphatase (V-PPase) might replace vacuolar H(+)-ATPase under energy stress due to anoxia or chilling in anoxia-tolerant species such as rice (Oryza sativa L.) and corn (Zea mays L.). The relative transcript level of V-PPase in rice seedlings, like that of alcohol dehydrogenase 1, increased greatly under anoxia and declined again when the seedlings were returned to air. However, the distribution of transcripts in root, shoot, and seed differed somewhat from that of alcohol dehydrogenase 1. Immunoreactive V-PPase protein and V-PPase enzyme specific activity in a tonoplast fraction from rice seedlings increased progressively with time of anoxia or chilling at 10 degrees C, showing a 75-fold increase after 6 d of anoxia, compared with a 2-fold increase of vacuolar H(+)-ATPase activity. When the seedlings were returned to air, the specific activity returned to its initial level within 2 d. After 6 d of chilling at 10 degrees C, V-PPase specific activity reached a level 20-fold of that at 25 degrees C. In microsomes of corn roots, V-PPase specific activity did not respond to anoxia but was constitutively high. It is proposed that V-PPase can be an important element in the survival strategies of plants under hypoxic or chilling stress.
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PMID:Vacuolar H(+)-translocating pyrophosphatase is induced by anoxia or chilling in seedlings of rice. 761 Jan 61

1-Hydroxyethane-1,1-diphosphonate (EHDP) and a variety of other diphosphonates, and also pyrophosphate, at millimolar levels were found to inhibit the growth of Streptococcus mutans GS-5. Inhibition appeared to be due mainly to chelation of Mg2+ and could be readily reversed through addition of Mg2+, or less effectively, by other divalent cations. The trianionic forms of the diphosphonates or pyrophosphate were more effective inhibitors than the dianionic forms. Diphosphonates and pyrophosphate did not inhibit glycolysis by S. mutans, assayed in terms of glucose utilization, or arginolysis by Streptococcus rattus FA-1, assayed in terms of ammonia production. However, they did act as buffers to moderate pH changes. Diphosphonates also were inhibitors of the F-ATPase of S. mutans by complex mechanisms only partly reversible with divalent cations. They also were inhibitors of the pyrophosphatase of the organism. However, intact cells were impermeable to the compounds, and inhibition of cytoplasmic or membrane enzymes did not appear to be involved in growth inhibition.
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PMID:Inhibition of streptococcal growth, F-ATPase and pyrophosphatase by diphosphonates. 764 73

Saccharomyces carlsbergenis vacuoles possess an ATPase activity differing from those of the well-known H(+)-ATPase of plasma membranes and mitochondria as well as from those of other phosphohydrolases. Yeast vacuolar ATPase represents an electrogenic H(+)-translocase. H(+)-ATPase was incorporated into a liposomal membrane in a functionally active form. Tonoplast ATPase did not form a phosphorylated intermediate. Purified vacuolar ATPase contained three major polypeptides with M(r) of 72, 62 and 16 kDa. S. carlsbergensis vacuoles also contained a pyrophosphatase (PPase) whose properties differed significantly from those of other vacuolar phosphohydrolases. Vacuolar membrane-bound PPase is a proton pump; its molecular mass is about 120 kDa. The enzyme molecule consists of three subunits, each of M(r) = 41 kDa. Soluble PPase from vacuolar sap has a molecular mass of about 82 kDa and consists of three subunits of M(r) = 28 kDa.
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PMID:[H+-ATPase and H+-pyrophosphatase in yeast vacuolar membrane]. 765 63

ATPase and inorganic pyrophosphatase (PPase) activities have been detected in several methanogenic bacteria. These activities are believed to play a crucial role in energy metabolism. In the present study we have investigated some characteristics of the ATPase and the inorganic PPase activities of Methanobacterium thermoautotrophicum. Although these proteins migrate identically on non-dissociating gels, they are catalyzed by distinct enzymes which are separable by biochemical purification methods. The partially purified enzymes are composed of at least two subunits. The ATPase subunits have molecular masses of about 43 and 33 kDa and the inorganic PPase such of about 31 and 25 kDa. After purification, the PPase and the ATPase did not hydrolyze ATP and PP(i), respectively. The membrane-bound ATPase and PPase activities are distinguished in response to sodium fluoride, by the effects of divalent cations, by the temperature ranges for activities and the solubilization behaviour by different extractants. Most investigated catalytic and structural properties of the ATPase do not suit the current criteria for classifying this enzyme under either the F-, V- or P-ATPases.
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PMID:Characterization and partial purification of an ATPase and inorganic pyrophosphatase of the archaebacterium Methanobacterium thermoautotrophicum. 794 42


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