Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ureaplasma urealyticum cells were lysed by osmotic shock or by digitonin. The membrane fraction contained four to ten times as much protein as the cytoplasmic fraction. These values are in large excess of those reported for classical mycoplasmas, suggesting that the Ureaplasma membrane fraction was heavily contaminated with proteins derived from the growth medium. The U. urealyticum urease activity was localized in the cytoplasmic fraction, whereas the adenosine triphosphatase activity was localized in the membrane fraction. Significant urease activity could be detected also in nonviable cells. Urea, at concentrations above 0.25 M, was mycoplasmastatic to Acholeplasma laidlawii, Mycoplasma hominis, and U. urealyticum, so that the Ureaplasma urease did not afford preferential protection against urea toxicity. The intracellular localization of the urease would be expected to release ammonia from urea in the cytoplasm. The ammonia will take up protons to become ammonium ions. It can be hypothesized that the intracellular NH4+ plays a role in proton elimination or acid-base balance, which might be coupled to an energy producing ion gradient and/or transport mechanisms.
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PMID:Localization of enzymes in Ureaplasma urealyticum (T-strain mycoplasma). 1 80

A spin-labeled ATP analogue, 2,2,6,6-tetramethylpiperidine-1-oxyl adenosine triphosphatase (Tempo-ATP) is used to adenylate Escherichia coli glutamine synthetase (L-glutamine: ammonia ligase (ADP-forming), EC 6.3.1.2). The Tempo adenylylated glutamine synthetase (Tempo-GS) exhibits similar catalytic properties, pH profile and inhibitor susceptibility as those of glutamine synthetase adenylylated with normal ATP. Using the spin label on the enzyme as a probe and employing the spin-spin interactions between the label probe and paramagnetic Mn2+, the distances from the nitroxyl moiety of the covalently bound Tempo-AMP to the two Mn2+ binding sites, n1 and n2 were determined. The n1 site is the structural site and n2 is located at the catalytic site. The distances from Mn2+ at n1 and n2 sites to the nitroxyl radical are 19 and 16 A, respectively. Binding of the substrate, L-Glu, causes a protein conformational change which is reflected by the reduction of approximately 2 A for the n1 to Tempo-AMP distance and lengthening of approximately 2 A for the n2 to the Tempo-AMP distance. Addition of ATP to the Tempo-GS/L-Glu complex increases the distance between n1 and Tempo-AMP, and n2 and Tempo-AMP by 4 and 3 A, respectively.
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PMID:Distance changes at the regulatory and catalytic sites on Escherichia coli glutamine synthetase: a spin label study on the effect of substrate(s) binding. 167 11

The homogeneity or heterogeneity at the enzyme level of mitochondria has not been directly demonstrated and is important for many studies. To clarify this point, carbamoyl phosphate synthase (ammonia), glutamate dehydrogenase and mitochondrial adenosine triphosphatase (F1) were located in rat liver by immunolabeling using protein A-gold. Measurements of the number of gold particles per square micron of cross sectional images of mitochondria permit to assess the relative molecular concentration of the three enzymes and, most interestingly, it presents the first evidence that different mitochondria in rat liver cells have the same relative proportion of the three enzymes. Since they have vastly different half-lives, bulk or unregulated autophagy as the main mechanism regulating the turnover of these enzymes seems unlikely.
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PMID:Homogeneity among mitochondria revealed by a constant proportion of their enzymes. 623 64

Sodium vanadate is a potent inhibitor of Na-K-adenosine triphosphatase. p-Aminohippurate (PAH) and tetraethylammonium accumulation in rat renal cortical slices was inhibited by vanadate in a dose-dependent manner at medium vanadate concentrations from 10(-6) to 10(-3) M. Inhibition was reversible at vanadate concentrations less than 1.5 x 10(-5) M. The slice content of vanadium (7.5-325 micrometer V/g wt. of tissue) was linearly related to medium vanadate concentrations ranging from 10(-5) to 10(-3) M. The ability of slices to generate glucose and ammonia was not impaired by medium vanadate concentrations up to 5 x 10(-4) M, a concentration that maximally inhibited organic ion accumulation. Increasing medium K+ concentrations potentiated vanadate inhibition of PAH accumulation which correlated with inhibition of sodium pump activity, as determined by 42K+ uptake. Intraperitoneal administration of vanadate (1 or 5 mg V/kg) to rats produced a profound diuresis and natriuresis during the 1st hr. Inhibition of PAH accumulation of renal slices from these rats was related to tissue vanadium concentrations. These data suggest that vanadate exerts its action on proximal tubule transport of PAH via inhibition of Na-K-adenosine triphosphatase.
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PMID:Effects of vanadate on organic ion accumulation in rat renal cortical slices. 691 88

Development of a bioartificial renal tubule with a confluent monolayer of renal epithelial cells supported on a permeable synthetic surface may be the first step to further optimization of renal substitution therapy currently used with hemodialysis or hemofiltration. Madin-Darby canine kidney cells, a permanent renal epithelial cell line, were seeded into the lumen of single hollow fibers. Functional confluence of the cells was demonstrated by the recovery of intraluminally perfused 14C-inulin that averaged >98.9% in the cell lined units vs <7.4% in the control noncell hollow fibers during identical pressure and flow conditions. The baseline absolute fluid transport rate averaged 1.4+/-0.4 microl/30 min. To test the dependency of fluid flux with oncotic and osmotic pressure differences across the bioartificial tubule, albumin was added to the extracapillary space, followed by the addition of ouabain, an inhibitor of Na+K+ adenosine triphosphatase, the enzyme responsible for active transport across the renal epithelium. Addition of albumin resulted in a significant increase in volume transport to 4.5+/-1.0 microl/30 min. Addition of ouabain inhibited transport back to baseline levels of 2.1+/-0.4 microl/30 min. These results are the first demonstration that renal epithelial cells have been grown successfully as a confluent monolayer along a hollow fiber, and exhibit functional transport capabilities. The next steps in constructing a bioartificial renal tubule successfully are to develop a multi-fiber bioreactor with primary renal proximal tubule cells that maintain not only transport properties but also differentiated metabolic and endocrine functions, including glucose and ammonia production, and the conversion of vitamin D3 to a more active derivative. A renal tubule device may add critical renal functional components not currently substituted for, thereby improving the treatment regimens for patients with acute and chronic renal failure.
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PMID:Tissue engineering of a bioartificial renal tubule. 961 48

Adult crayfish (Cambarus diogenes diogenes) exposed to 8.41 +/- 0.17 microg silver/L (19.4% as Ag+) in moderately hard freshwater under flow-through conditions for 96 h exhibited ionoregulatory disturbance, elevated metabolic ammonia (T(amm)) production and substantial silver accumulation in the gills, hemolymph, and hepatopancreas. The ionoregulatory disturbance included both a generally reduced unidirectional Na+ influx and an increased unidirectional Na+ efflux, leading to a substantial net loss of Na+ from the silver-exposed crayfish. The Na+ uptake in silver-exposed crayfish differed overall from controls, while the increased Na+ efflux recovered to control values 48 h into the 96 h of exposure. The general inhibition of Na+ uptake could be explained by a reduced sodium/potassium-adenosine triphosphatase (Na/K-ATPase) activity in terminally obtained gill samples from the silver-exposed crayfish. The silver-induced effect on Na+ uptake and loss translated to reduced hemolymph Na+ concentrations but not significantly reduced hemolymph Cl- concentrations. Hemolymph T(anim) and T(amm) efflux both increased in silver-exposed crayfish, indicating an increased metabolic T(amm) production. The present study demonstrates that the toxic mechanism of waterborne silver exposure in freshwater crayfish resembles that of freshwater teleost fish. The crayfish might therefore be a useful model system for extending current environmental regulatory strategies, currently based on teleost fish, to invertebrates.
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PMID:Physiological responses to acute silver exposure in the freshwater crayfish (Cambarus diogenes diogenes)--a model invertebrate? 1183 7

Several methods for removing interfering nucleotides, adenosine-5'-monophosphate and adenosine 5'-triphosphate from brain extracts have been studied. An enzymic method, using adenylic acid deaminase, has been found suitable. This deaminates adenosine monophosphate to 5'-inosinic acid, an inactive compound which does not influence the estimations of substance P. Owing to the adenosine triphosphatase content of the enzyme extract, adenosine triphosphate was also inactivated. For the estimation of adenosine monophosphate-deaminase activity, a simple colorimetric method is described which measures the ammonia liberated from adenosine monophosphate. Substance P in mouse brain extracts was estimated after treatment of the animals with various drugs, and after the enzymic removal of interfering nucleotides from the brain extracts. The drugs had no effect on the substance P content of mouse brain. The effect of drugs on the contractions of the guinea-pig ileum induced by substance P was also investigated, and the effect of drugs on the estimations of substance P in brain extracts is discussed.
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PMID:REMOVAL OF INTERFERING NUCLEOTIDES FROM BRAIN EXTRACTS CONTAINING SUBSTANCE P. EFFECT OF DRUGS ON BRAIN CONCENTRATIONS OF SUBSTANCE P. 1406 36

Adenosine triphosphate (ATP) hydrolysis in the nitrogenase complex controls the cycle of association and dissociation between the electron donor adenosine triphosphatase (ATPase) (Fe-protein) and its target catalytic protein (MoFe-protein), driving the reduction of dinitrogen into ammonia. Crystal structures in different nucleotide states have been determined that identify conformational changes in the nitrogenase complex during ATP turnover. These structures reveal distinct and mutually exclusive interaction sites on the MoFe-protein surface that are selectively populated, depending on the Fe-protein nucleotide state. A consequence of these different docking geometries is that the distance between redox cofactors, a critical determinant of the intermolecular electron transfer rate, is coupled to the nucleotide state. More generally, stabilization of distinct docking geometries by different nucleotide states, as seen for nitrogenase, could enable nucleotide hydrolysis to drive the relative motion of protein partners in molecular motors and other systems.
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PMID:Nitrogenase complexes: multiple docking sites for a nucleotide switch protein. 1612 1

Two waterborne Cu exposures were performed to investigate if Cu is an ionoregulatory toxicant at all salinities in the killifish, Fundulus heteroclitus. A 30-day flow through exposure in 0 (FW), 5, 11, 22, and 28 ppt (SW) and three [Cu]'s (nominal 0, 30, and 150 microg Cu L(-1)) revealed no apparent Cu induced mortality at the intermediate salinities and high mortality in FW and SW. Fish were sampled at 4, 12, and 30 days after the start of the exposure and both Na+/K+ adenosine triphosphatase (Na+/K+ ATPase) and carbonic anhydrase (CA) activity in the gill and intestine as well as whole body [Na+], and [Cl-] were measured. At the high [Cu] a reduction of whole body [Na+] after 4 days of exposure in FW was the only physiological parameter influenced. A second static 24h Cu exposure was performed in FW, 5, 13, and 29 ppt (SW) and two [Cu]'s (nominal 0 and 110 microg Cu L(-1)). In addition to the parameters listed above, ammonia flux was measured at all salinities and Na+ flux was measured in FW fish. Cu affected ionoregulation in FW where decreased Na+ uptake associated with inhibition of Na+/K+ ATPase led to decreased whole body [Na+] after 24h. The only affected parameter in SW was net ammonia excretion suggesting that Cu is not an ionoregulatory toxicant in SW at the concentrations employed. We propose that physiology rather than chemistry explain much of the variation in Cu toxicity seen across salinities.
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PMID:Copper toxicity across salinities from freshwater to seawater in the euryhaline fish Fundulus heteroclitus: is copper an ionoregulatory toxicant in high salinities? 1699 24

Eel aquaculture is capture based and thus dependent on the fishery for juvenile glass eels. This fishery typically takes place in estuaries where salinity varies and ammonia levels can be elevated. Also, during capture and transport glass eels are kept at high densities and ammonia from endogenous production can increase to toxic levels. Ammonia is known to have detrimental effects on fish growth and survival. In the present study, the salinity dependence of ammonia sensitivity in glass eels acclimated to either seawater or freshwater was determined, and the possible role of branchial sodium/potassium adenosine triphosphatase (Na+/K+ -ATPase) was investigated. Freshwater-acclimated glass eels were found to be more sensitive to ammonia with a lethal concentration to 50% of the test organisms (LC50) value for 96 h of 3.30 mM for total ammonia nitrogen (TAN) and 117 microM for un-ionized ammonia (UIA), versus values of 4.95 mM and 138 microM, respectively, for seawater-acclimated animals. Freshwater glass eels also had significantly lower body TAN levels than seawater-acclimated glass eels, although body accumulation profiles during exposure were similar. The higher branchial Na+/K+ -ATPase activities in seawater glass eels might explain this difference in sensitivity; however, activities decreased significantly with increasing ammonia levels. There was also no salinity dependence of net ammonia flux rates (0.388 micromol of TAN/g/h). Holding glass eels at high densities characteristic of transport conditions resulted in elevated ammonia concentrations to approximately 3 mM, which coincidently approaches to the freshwater LC50 value and may therefore contribute to mortality.
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PMID:Ammonia sensitivity of the glass eel (Anguilla anguilla L.): salinity dependence and the role of branchial sodium/potassium adenosine triphosphatase. 1871 20


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