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)

Sarcoplasmic reticulum (SR) of high purity and functional integrity was isolated from skeletal muscle of normal and ethanol-tolerant rats. Ethanol at low concentrations (0.1 to 0.2 M), added in vitro to isolated SR, resulted in slight inhibition of both calcium loading and calcium-stimulated ATPase rates. Higher concentrations of ethanol resulted in further inhibition of calcium loading, but not of calcium-stimulated ATPase. Fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) in isolated SR membranes showed a small decrease in anisotropy with the addition of ethanol in vitro. Sarcoplasmic reticulum from normal and ethanol-tolerant rats did not differ in calcium pump function or in fluorescence polarization of DPH, in the presence or absence of ethanol.
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PMID:Calcium transport and fluorescence polarization of 1,6-diphenyl-1, 3,5-hexatriene in sarcoplasmic reticulum from normal and ethanol-tolerant rats. 622 40

Data are presented that lead to an alternative model for the organization and molecular dynamics of lipid molecules near the Ca2+-stimulated, Mg2+-dependent adenosinetriphosphatase (Ca2+-ATPase; ATP phosphohydrolase, EC 3.6.1.3) of sarcoplasmic reticulum. Measurements of the steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene in progressively delipidated sarcoplasmic reticulum membranes have been quantitatively interpreted in terms of a layer of lipid of high anisotropy (the lipid annulus) coexisting with lipid layers of very low anisotropy. In addition, the Ca2+-ATPase has been reconstituted into pure 1,2-dipentadecanoyl 3-sn-phosphatidylcholine membranes over a range of lipid-to-protein ratios. High-sensitivity differential scanning calorimetry has demonstrated that roughly 30 lipid molecules per Ca2+-ATPase molecule (annular lipids) fail to undergo a calorimetrically detectable phase transition in the temperature range 4-44 degrees C. Roughly 100 lipid molecules beyond the annulus undergo a detectable phase transition at a temperature below the phase transition of pure lipid and with an enthalpy change [4.2 kcal/mol (1 kcal = 4.18 kJ)] about half that observed for pure lipid vesicles (7.7-7.8 kcal/mol). We propose that both the fluorometric and calorimetric data are consistent with a model in which a motionally inhibited lipid annulus is surrounded by a more extensive region of disrupted lipid packing order, which we have called the secondary lipid domain.
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PMID:Ordered and disordered phospholipid domains coexist in membranes containing the calcium pump protein of sarcoplasmic reticulum. 622 75

I have recently reported the isolation and characterization of sarcoplasmic reticulum from normal and dystrophic mice. These sarcoplasmic reticulum fractions were similar in calcium pump function, calcium release properties, and lipid composition. In this report, I describe the isolation of mouse muscle transverse tubule membranes using a calcium phosphate-loading technique. When the relative purity of normal and dystrophic preparations was considered, transverse tubule from normal and dystrophic mice were similar in calcium-insensitive ATPase activity, cholesterol content, and membrane microviscosity (as estimated by fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene); transverse tubule yield from dystrophic muscle, however, was twice that from normal muscle, while sarcoplasmic reticulum yield from these same dystrophic muscles was only 60% that from normal muscle. This result may reflect a difference in the relative quantities of these membranes in situ.
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PMID:Isolation and characterization of transverse tubule from normal and dystrophic mice. 623 25

After exposure of HeLa cells to poliovirus there is a rapid decline (within minutes) in fluorescence polarization of DPH (1,6-diphenyl-1,3,5-hexatriene). Within one hour after infection the (Na+/K+)ATPase activity of an isolated plasma-membrane-rich fraction is enhanced, the cell volume decreases, and the intracellular concentration of a potent low-molecular-weight inhibitor of host protein synthesis increases.
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PMID:Alterations in plasma-membrane functions after poliovirus infection. 629 66

The partial purification of (Na+ + K+)-ATPase from pig lens has been achieved by treatment with deoxycholate followed by density gradient centrifugation. The specific activity of the final preparation, ranging from 300 to 500 nmol/h per mg protein, is increased approx. 100-fold compared to the homogenate. A parallel increase in rho-nitrophenylphosphatase activity is also observed. Sodium dodecyl sulfate (SDS) gel electrophoresis reveals six major protein bands, one of which is the 93 kDa alpha subunit of (Na+ + K+)-ATPase which can be phosphorylated by reaction with [gamma-32P]ATP. A second band contains a glycoprotein which displays an apparent molecular weight of 51000 and thus appears to be the beta subunit of the enzyme. The enzyme is sensitive to ouabain with the I50 for (Na+ + K+)-ATPase and rho-nitrophenylphosphatase inhibition being 1.2 and 1.3 microM, respectively. Several agents which inhibit (Na+ + K+)-ATPase from other tissues such as oligomycin, Ca2+, vanadate, N-ethylmaleimide, rho-chloromercuribenzenesulfonic acid (PCMBS) and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) also inhibit the lens enzyme. Monovalent cations other than K+ are partially effective in activating the (Na+ + K+)-ATPase and rho-nitrophenylphosphatase activities. The K+ congeners were relatively more effective in supporting (Na+ + K+)-ATPase compared to rho-nitrophenylphosphatase activity. Other kinetic properties of the lens enzyme are also comparable to those of the enzyme from other tissues. Utilizing the partially purified membrane bound enzyme, discontinuities in Arrhenius plots of (Na+ + K+)-ATPase activity, rho-nitrophenylphosphatase activity and fluorescence polarization of the fluidity probe, 1,6-diphenyl-1,3,5-hexatriene (DPH), are observed near the physiological temperature of lens. The possible significance of these observations for the mechanism of cataract formation are discussed.
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PMID:Characterization of partially purified (Na+ + K+)-ATPase from porcine lens. 629 83

We studied changes in hepatic membrane (Na+,K+)ATPase activity and membrane lipids induced by canrenoate, the water-soluble congener of canrenone, the active metabolite of spironolactone. (Na+,K+)ATPase activity was decreased after canrenoate in a dose- and time-dependent manner. Decreased activity was demonstrated at the lowest dose (91% of control after 5 mumoles per 100 gm body weight per day X 3 days); the maximum dose (30 mumoles per 100 gm body weight per day X 3 days) resulted in activity 38% of untreated control values. A 20 mumoles per 100 gm body weight per day dose decreased enzyme activity to 89 and 55% of control after 24 and 72 hr, respectively. The nonionic detergent Triton WR-1339 partially reversed drug-induced inhibition, suggesting that the enzyme changes may be related to altered membrane lipids. Membrane cholesterol increased 17% after 3 days of 30 mumoles canrenoate per 100 gm body weight per day; phospholipids decreased by 12%. The cholesterol to phospholipid molar ratio increased from 0.419 to 0.555. Membrane fluidity, as measured by the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene decreased after treatment with 20 mumoles canrenoate per 100 gm body weight per day for 3 days. These results describe in vivo and in vitro inhibition of hepatic (Na+,K+)ATPase activity. Increased membrane cholesterol with decreased phospholipid alters membrane fluidity and may be partially responsible for the change in (Na+,K+)ATPase activity.
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PMID:Spironolactone- and canrenone-induced changes in hepatic (Na+,K+)ATPase activity, surface membrane cholesterol and phospholipid, and fluorescence polarization in the rat. 630 16

Rats were maintained on a regimen of intermittent starvation followed by refeeding a fat-free diet in order to induce hepatic acyl desaturase activities and other enzymes involved in lipid synthesis. The effects of the dietary regimen on the lipid composition and fluidity of isolated hepatocyte plasma membranes were compared to corresponding effects on microsomal preparations. The dietary regimen increased the content of monoenoic and polyenoic acyl chains and decreased the cholesterol/phospholipid molar ratio in the plasma membranes. Accordingly, the lipid fluidity of the plasma membranes was significantly increased as assessed by the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene and 12-(9-anthroyloxy)stearate and the intramolecular excimer fluorescence of 1,3-di(1-pyrenyl)propane. In the microsomal membranes, substantial increases in the content of monoenoic acyl chains were offset by decreases in polyenoic acids, and no change in cholesterol/phospholipid ratio was observed. Correspondingly, the lipid fluidity of the microsomal membranes remained almost unchanged. The enhancement of lipid fluidity in the hepatocyte plasma membranes was accompanied by an increase of approximately 68% in the specific activity of the (Na+ + K+)-dependent adenosinetriphosphatase. The results demonstrate that a dietary regimen can modulate in vivo the lipid composition, fluidity, and enzyme function of the hepatocyte plasma membrane.
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PMID:Dietary induction of acyl chain desaturases alters the lipid composition and fluidity of rat hepatocyte plasma membranes. 632 63

The lipid composition and fluidity of basolateral membranes prepared from the mucosa of the proximal, middle and distal thirds of the rat small intestine were determined. Fluidity, as assessed by the fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene and a series of anthroyloxy fatty acid derivatives, is decreased in the distal third as compared to the proximal segments. This pattern is similar to that described previously for microvillus membranes. The decrease in fluidity of the distal as compared to the proximal membranes results from an increase in cholesterol content, cholesterol/phospholipid molar ratio and degree of saturation of the fatty acid residues. In the middle and distal thirds of the gut, the degree of saturation of the fatty acid residues is higher in microvillus as compared to basolateral membranes, accounting in part for the characteristically lower fluidity of the luminal membranes. The specific activity of the basolateral membrane (Na+ + K+)-dependent adenosine triphosphatase is significantly lower in the distal as compared to the proximal and middle thirds of the intestinal mucosa. Studies of the binding of [3H]ouabain indicate that this pattern results from fewer enzyme sites in the distal membranes.
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PMID:Lipid composition and fluidity of rat enterocyte basolateral membranes. Regional differences. 632 92

Plasma membranes, microsomes, and mitochondria were isolated from paired, passage number matched, cultured human fibroblasts. The cells were obtained from skin biopsies of Huntington's disease (HD) subjects and from sex and age matched controls. All fibroblasts were cultured in identical media for three to seven passages. Enrichment of surface marker enzymes such as Na+,K+-ATPase indicated a 10-fold purification of the isolated plasma membrane. The specific activity of Na+,K+-ATPase was 62 and 82% greater in the crude homogenate and isolated plasma membrane, respectively, of HD fibroblasts than in control fibroblasts. The specific activity of plasma membrane Na+,K+-ATPase was correlated with lipid composition and with membrane structure as determined by measurement of the rotational relaxation time and limiting anisotropy of fluorescence probe molecules. Major alterations in the structure of the plasma membranes in HD fibroblasts were not noted. The rotational relaxation time and limiting anisotropy of 1,6-diphenyl-1,3,5-hexatriene and of trans-parinaric acid were not significantly different between the plasma membrane, microsomes, or mitochondria of HD versus those of control fibroblasts. trans-Parinaric acid demonstrated the coexistence of fluid and solid domains in all three subcellular membrane fractions of the normal and HD skin fibroblasts. Lastly, both trans-parinaric acid and 1,6-diphenyl-1,3,5-hexatriene displayed characteristic breakpoints in Arrhenius plots of absorbance corrected fluorescence in plasma membranes, microsomes, and mitochondria. In all cases, similar breakpoint temperatures, indicative of phase alterations, were noted near 20 degrees and 30 degrees C. These breakpoints were unaltered in HD. In summary, the data do not support the concept of major membrane structural defects in HD.
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PMID:Membrane anomalies in Huntington's disease fibroblasts. 633 Mar 2

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


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