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)

We performed analytical fractionation studies with the goal of isolating basal-lateral and apical membrane vesicles from epithelial cells of rat exorbital lacrimal gland. A density region designated window II contained elements of three physically and biochemically distinct membrane populations. These were resolved by countercurrent distribution in an aqueous polymer two-phase system. One population contained 50% of the NADPH-cytochrome c reductase activity recovered from window II and appeared to be of intracellular origin. A second population contained 70% of the recovered Na-K-ATPase, maximally enriched 42-fold with respect to the initial homogenate. This population was the major locus of alanine transport activity, roughly 85% of which was mediated by systems believed to be characteristic of epithelial cell basal-lateral membranes. It also contained portions of the alkaline phosphatase, galactosyltransferase, acid phosphatase, and NADPH-cytochrome c reductase activities. A third population accounted for 33% of the recovered alkaline phosphatase and was a secondary locus of Na-alanine transport activity, 45% of which could be attributed to systems believed to be characteristic of epithelial cell apical membranes.
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PMID:Resolution of apical and basal-lateral membrane populations from rat exorbital gland. 631 24

A microsomal fraction was isolated from guinea pig taenia caecum by differential centrifugation. Activities of ouabain-sensitive (Na+, K+)-ATPase, 5'-nucleotidase and NADPH-cytochrome c reductase were enriched in the microsomal fraction. On the other hand, less cytochrome c oxidase and monoamine oxidase were contained in this fraction. These results suggest that the microsomal fraction used in this study was derived from both sarcolemma and sarcoplasmic reticulum. Ca2+ uptake by this fraction was strictly dependent on the presence of ATP and was facilitated by oxalate. An ATP-regenerating system was required for the determination of Ca2+ uptake, when a lower concentration of ATP (e.g. 0.25 mM) was used. Phosphorylation of the microsomal fraction was doubled when these membranes were incubated in the presence of cyclic AMP plus cyclic AMP-dependent protein kinase (protein kinase). When the microsomal fraction was pretreated with cyclic AMP plus protein kinase, Ca2+ uptake was stimulated. The increases in microsomal phosphorylation and Ca2+ uptake were significantly correlated (P less than 0.01). This stimulation of Ca2+ uptake by microsomal phosphorylation was observed only in the presence of protein kinase, oxalate, and low Ca2+ and Mg2+ concentrations. The results suggest that stimulation of Ca2+ uptake may be the mechanism by which cyclic AMP is involved in beta-adrenergic relaxation of smooth muscle.
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PMID:Effects of cyclic AMP and protein kinase on calcium uptake in a microsomal fraction from guinea pig taenia caecum. 631 21

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

Distribution of specific binding sites for [3H]nitrendipine was studied in subcellular fractions isolated from rat gastric fundus smooth muscle and from rat myometrium. There was an excellent correlation between the distribution of [3H]nitrendipine binding determined at the nitrendipine concentrations of 0.138 and 1.38 nM, and the distribution of the plasma membrane markers K+-activated ouabain-sensitive p-nitrophenylphosphatase, 5'-nucleotidase, phosphodiesterase I, and Mg-ATPase, but not between the mitochondrial markers cytochrome c, oxidase, succinate-dependent cytochrome c reductase, or rotenone-insensitive NADH-dependent cytochrome c reductase or the putative endoplasmic reticulum marker NADPH-dependent cytochrome c reductase. The binding occurred with high affinity and with a similar (0.097-0.146 nM) equilibrium dissociation constant to all the fractions, even though the density of binding sites varied and was highest in the plasma membrane marker-enriched fractions. The maximal binding in the plasma membrane-enriched fraction from the rat gastric fundus smooth muscle was 0.43 +/- 0.04 pmol/mg, and in that from rat myometrium was 0.72 +/- 0.09 pmol/mg. Thus in the two smooth muscles studied the plasma membrane is the locus of the high affinity nitrendipine binding.
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PMID:Subcellular distribution of [3H]nitrendipine binding in smooth muscle. 632 63

Membrane enzyme activities, lipid composition, and fluorescence probe characteristics in isolated plasma membranes, microsomes and mitochondria of cultured human fibroblasts were used to determine if structural alterations occurred as a function of donor age. The cells were sex matched and allowed to undergo approximately 8 population doublings under identical culture conditions. Plasma membrane (Na+, K+)-ATPase, microsomal NADPH cytochrome c reductase, and mitochondrial succinate cytochrome c activities showed variation as a function of increasing donor age but these changes were not statistically significant. At the same time the cholesterol/phospholipid molar ratio was unaltered in plasma membranes, decreased 50% in microsomes, and unchanged in mitochondria with increasing donor age. The phosphatidylcholine/phosphatidylethanolamine ratio increased in all three membrane fractions with increasing age of the fibroblast donor. The ratio of unsaturated/saturated fatty acids decreased in the phospholipids of microsomes but not of plasma membranes or mitochondria. The structural properties of the membranes were determined with two different fluorescence probe molecules, trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene. These probe molecules indicated that the fluorescence lifetime and/or fluorescence polarization of the trans-parinaric acid probe decreased in microsomes, mitochondria, and in the plasma membrane, such that the limiting anisotropy, indicative of restrictions to probe motions, was significantly lower (high fluidity) with increasing subject age in plasma membranes, microsomes and mitochondria. The trans-parinaric acid fluorescence lifetime displayed two components in plasma membranes, microsomes, and mitochondria, a finding consistent with the coexistence of fluid and solid membrane lipid areas in the cultured human fibroblast subcellular membranes. The trans-parinaric acid partitioned preferentially into solid membrane areas. The limiting anisotropy of 1,6-diphenyl-1,3,5-hexatriene, a fluorescent probe that partitioned almost equally into different lipid domains, was also decreased in microsomes and mitochondria with increasing donor age. In contrast, 1,6-diphenyl-1,3,5-hexatriene indicated a small increase in limiting anisotropy (0.219 vs 0.195) in plasma membranes. Arrhenius plots of trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene absorbance-corrected fluorescence in plasma membranes, microsomes and mitochondria demonstrated characteristic breakpoints near 20 degrees C and 30 degrees C. These breakpoints were not altered as a function of age.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Age-related alterations in cultured human fibroblast membrane structure and function. 633 Apr 63

A conventional brush border membrane preparation, obtained by divalent cation precipitation of homogenates of rabbit renal cortex, was analyzed by countercurrent distribution in an aqueous dextran:polyethylene glycol two-phase system. The resulting fractions were assayed for the presence of the Na+/H+ antiporter and for a variety of biochemical marker enzymes. This analysis revealed four physically distinct membrane populations (A-D). Population A consisted of two subpopulations, A' and A", which were enriched an average of 49-fold in maltase; they were also highly enriched in alkaline phosphatase, leucine aminopeptidase, and Na+/H+ antiporter. On the basis of their marker contents, populations A' and A" appear to represent highly purified, functional brush border membrane vesicles. Population B was enriched twofold in NADPH-cytochrome c reductase and population C was enriched 12-fold in galactosyltransferase. Populations B and C accounted for 25% of the protein in the starting material and appear to reflect contamination of the brush border membrane preparation by subpopulations of endoplasmic reticulum and Golgi fragments. Population D was enriched in Na+/H+ antiporter, alkaline phosphatase, leucine aminopeptidase, Na-K-ATPase, and acid phosphatase but not maltase, NADPH-cytochrome c reductase, galactosyltransferase, or succinate dehydrogenase. Its identity is unclear, and it might consist of a multiplicity of populations from different origins.
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PMID:Na+/H+ antiporter in membrane populations resolved from a renal brush border vesicle preparation. 633 Nov 75

We have previously shown that inositol-1,4,5-trisphosphate (IP3) releases Ca2+ from an intracellular calcium store in permeabilized acinar cells of rat pancreas (H. Streb et al., 1983, Nature (London) 306:67-69). This observation suggests that IP3 might provide the missing link between activation of the muscarinic receptor and Ca2+ release from intracellular stores during stimulation. In order to localize the intracellular IP3-sensitive calcium pool, IP3-induced Ca2+ release was measured in isolated subcellular fractions. A total homogenate was prepared from acinar cells which had been isolated by a collagenase digestion method. Endoplasmic reticulum was separated from mitochondria, zymogen granules and nuclei by differential centrifugation. Plasma membranes and endoplasmic reticulum were separated by centrifugation on a sucrose step gradient or by precipitation with high concentrations of MgCl2. IP3-induced Ca2+ release per mg protein in the total homogenate was the same as in leaky cells and was sufficiently stable to make short separation procedures possible. In fractions obtained by either differential centrifugation at 7000 X g, sucrose-density centrifugation, or MgCl2 precipitation there was a close correlation of Ip3-induced Ca2+ release with the endoplasmic reticulum markers ribonucleic acid (r = 0.96, 1.00, 0.91, respectively) and NADPH cytochrome c reductase (r = 0.63, 0.98, 0.90, respectively). In contrast, there was a clear negative correlation with the mitochondrial markers cytochrome c oxidase (r = -0.64) and glutamate dehydrogenase (r = -0.75) and with the plasma membrane markers (Na+ + K+)-ATPase (r = -0.81) and alkaline phosphatase (r = -0.77) in all fractions analyzed. IP3-induced Ca2+ release was distributed independently of zymogen granule or nuclei content of the fractions as assessed by electron microscopy. The data suggest that inositol-1,4,5-trisphosphate releases Ca2+ from endoplasmic reticulum in pancreatic acinar cells.
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PMID:Effect of inositol-1,4,5-trisphosphate on isolated subcellular fractions of rat pancreas. 633 62

Ca2+-dependent K+ transport and plasma membrane NADH dehydrogenase activities have been studied in several 'high-K+' (human, rabbit and guinea pig) and 'low-K+' (dog, cat and sheep) erythrocytes. All the species except sheep showed Ca2+-dependent K+ transport. NADH-ferricyanide reductase was detected in all the species and showed positive correlation with the flavin contents of the membranes. NADH-cytochrome c reductase was very low or absent in dog, sheep and guinea pig membranes. No correlation was found between NADH dehydrogenase and Ca2+-dependent K+ channel activities in the species studied. Nor were any of the above activities correlated with (Na+ + K+)-ATPase activity.
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PMID:Plasma membrane nadh dehydrogenase and Ca2+-dependent potassium transport in erythrocytes of several animal species. 640 2

Bilirubin in different concentrations was injected in newborn guinea-pigs and the following parameters were determined: serum total and unbound bilirubin, whole brain bilirubin content and oxygen consumption, NADH-cytochrome c reductase and ATPase activities in brain mitochondria. The results showed a significant correlation between decreased rates of brain metabolism and the elevation of serum total and unbound bilirubin.
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PMID:The serum levels of unbound bilirubin that induce changes in some brain mitochondrial reactions in newborn guinea-pigs. 645 26

The effects of citrinin, ochratoxin A, or a combination of the two mycotoxins on the hepatic monooxygenase system and on hepatic and renal adenosinetriphosphatase (ATPase) activities were examined in neonatal rats exposed to a single treatment of one or both toxins. Animals received (po) 25 mg/kg citrinin, 1 mg/kg ochratoxin A, or 25 mg/kg citrinin plus 1 mg/kg ochratoxin A within 24 h of birth. Pups were killed 12 d later. Citrinin or ochratoxin A alone did not affect hepatic ATPase. Renal oligomycin-sensitive Mg2+-ATPase was inhibited to the same degree by ochratoxin A and the combination treatment. A synergistic effect of the two mycotoxins was observed on renal Na+-K+-ATPase. Significant effects, due to the mycotoxin interaction, were also observed on cytochrome P-450 content, NADPH-dependent dehydrogenase, and NADPH-cytochrome c reductase.
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PMID:Effects of the mycotoxins citrinin and ochratoxin a on hepatic mixed-function oxidase and adenosinetriphosphatase in neonatal rats. 646 Jan 15


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