Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphorylation of the calcium-transport ATPase of skeletal muscle sarcoplasmic reticulum by inorganic phosphate was investigated in the presence or absence of a calcium gradient. The maximum phosphoprotein formation in the presence of a calcium gradient at 20 degrees C and pH 7.0 is approximately 4 nmol/mg sarcoplasmic reticulum protein, but only between 2.4 and 2.8 nmol/mg protein in the absence of a calcium gradient, using Ionophore X-537 A or phospholipase-A-treated sarcoplasmic reticulum vesicles. Maximum phosphoprotein formation independent of calcium gradient at 20 degrees C and pH 6.2 is in the range of 3.6--4 nmol/mg protein. Half-maximum phosphoprotein formation dependent on calcium gradient was achieved with 0.1--0.2 mM free orthophosphate at 10 mM free magnesium or at 0.1--0.2 mM free magnesium at 10 mM free orthophosphate. Phosphoprotein formation independent of calcium gradient is in accordance with a model which assumes, firstly, the formation of a ternary complex of the ATPase protein with orthophosphate and magnesium (E . Pi . Mg) in equilibrium with the phosphoprotein (E-Pi . Mg) and, secondly, an interdependence of both ions in the formation of the ternary complex. The apparent equilibrium constant was 0.6 and the apparent dissociation constants KMg, KMg', KPi and KPi' were 8.8, 1.9, 7.2 and 1.5 mM respectively, assuming a total concentration of the phosphorylation site per enzyme of 7 nmol/mg protein.
 ...
PMID:Calcium gradient-dependent and calcium gradient-independent phosphorylation of sarcoplasmic reticulum by orthophosphate. The role of magnesium. 3 42

1. Haemoglobin-free erythrocyte ghosts were prepared in 40 imosM bicarbonate buffer, pH 7.4, containing 1 mM EDTA (40 imosM/l mM EDTA). The ghost preparation was highly permeable on preparation but partially resealed on incubation in media containing Ca-2+. 2. A partially purified preparation of phospholipase C from Clostridum welchii caused an increase in observed Mg-2+-ATPase activity, reflecting a change in the permeability of the ghost to substrate. The phospholipase did not decrease Mg-2+-ATPase even at the highest levels tested. Mg-2+-ATPase activity could therefore be used as a permeability indicatior in these experiments. 3. Both (Ca-2+, Mg-2+)-ATPase activities of the ghosts were progressively lost as a result of the phospholipid hydrolysis induced by phospholipase C. 4. When a haemolysin in the commercial preparation was destroyed by heat-treatment, deactivation of the (Ca-2+, Mg-2+)-ATPase and (Na+, K+, Mg-2+)-ATPases were still observed but permeability changes were greatly reduced. 5. The products of phospholipase action were not inhibitory to the Ca-2+, Mg-2+)-ATPase. 6. Lysolecithin brought about a reactivation of the (Ca-2+, Mg-2+)-ATPase which was superimposed upon permeability changes in the preparation. 7. Reactivation of the (Ca-2+, Mg-2+)-ATPase was brought about by a nonlytic, mixed lipid preparation without significant effect upon permeability. 8. Human erythrocyte (Ca-2+, Mg-2+)-ATPase therefore appears to be an enzyme which responds to perturbation of the lipid environment in the membrane and is a "lipid-dependant" enzyme.
 ...
PMID:Hydrolysis of erythrocyte membrane phospholipids by a preparation of phospholipase C from Clostridium Welchii. Deactivation of (Ca-2+, Mg-2+)-ATPase and its reactivation by added lipids. 12 73

Membranes were isolated and purified from nutrient broth-yeast extract- and hexadecane-grown cells of Acinetobacter sp. strain HO1-N. Two membrane fractions were isolated from nutrient broth-yeast extract-grown cells, the cytoplasmic membrane and the outer membrane. In addition to these two membrane fractions, a unique membrane fraction was isolated from hexadecane-grown cells (band 1) and characterized as a lipid-rich, low-density membrane containing high concentrations of hexadecane. The outer membrane preparations of Acinetobacter, obtained from nutrient broth-yeast extract- and hexadecane-grown cells, exhibited a low ratio of lipid phosphorus to protein and contained phospholipase activity and 2-keto-3-deoxyoctulosonic acid. Phosphatidic acid cytidyltransferase, adenosine triphosphatase, and reduced nicotinamide adenine dinucleotide oxidase were recovered almost exclusively in the cytoplasmic membrane fractions. The cytoplasmic membrane fractions contained 20 to 25 polypeptide species on sodium dodecyl sulfate-polyacrylamide gels, and the outer membrane fractions contained 15 to 20 polypeptide species. A major polypeptide species with an apparent molecular weight of approximately 42,000 to 44,000 was found for all outer membrane fractions. The buoyant densities of the cytoplasmic membrane fractions and the outer membrane fractions were closely similar, necessitating their separation by differential centrifugation. Band 1 of hexadecane-grown cells had a ratio of lipid phosphorus to protein that was almost twice that of cytoplasmic membrane and a correspondingly low buoyant density (1.086 g/cm3). Enzyme activities associated with band 1 were identical to those associated with the cytoplasmic membrane. The electrophoretic banding pattern of band 1 was essentially identical to the banding pattern of the cytoplasmic membrane. The phospholipid and neutral lipid compositions of the isolated membrane fractions were determined as qualitatively similar, with significant quantitative differences. The ultrastructure characteristics of the respective membrane fractions were examined by the negative-stain technique.
 ...
PMID:Isolation and characterization of membranes from a hydrocarbon-oxidizing Acinetobacter sp. 13 29

The phospholipid composition of oligomycin-sensitive ATPase fractions from mitochondria, precipitated under different ammonium sulfate concentrations according to the Kagawa-Racker method, was studied. The ATPase activity of the isolated fractions was found to be correlated with the levels of their phospholipase and esterase activities.
 ...
PMID:[Phospholipid composition and enzyme activity of mitochondrial ATPase complexes]. 15 50

1. For a period of 31 days male rats were given a liquid diet containing 36% of its energy as ethanol. Liver mitochondria from these animals demonstrated lowered respiratory control with succinate as substrate, a diminished energy-linked anilinonaphthalene-sulphonic acid fluorescence response, and lowered endogenous ATP concentrations. The phospholipid/protein ratio in mitochondria from these animals was unchanged; only minor alterations in the phospholipid fatty acid composition were observed. 2. In experiments where mitochondria were incubated at 18 degrees C in iso-osmotic sucrose (aging experiments), the above energy-linked properties were lost at an earlier time in organelles from ethanol-fed animals. Phospholipase A2 acitivty was depressed in mitochondria from control animals until respiratory control was lost and ATP was depleted. In contrast, no lag in the expression of phospholipase activity was observed in mitochondria from ethanol-fed rats. This loss of control of the phospholipase resulted in an earlier degradation of membrane phospholipids under the conditions of the aging experiments. 3. The ATPase (adenosine triphosphatase) activities, measured in freshly prepared tightly coupled mitochondria and in organelles uncoupled with carbonyl cyanide p-trifluoromethoxyphenylhydrazone, were not significantly different in ethanol-fed and liquid-diet control animals. When the mitochondria were aged at 18 degrees C, the activity increased with time of incubation in organelles from both groups of animals. A lag was observed, however, as the ATPase activity increased in control preparations. This lag was not present as APTase activity increased in mitochondria from ethanol-fed animals. 4. The significantly lowered values observed for energy-linked functions with succinate as an energy source demonstrate that ethanol elicits an alteration in liver mitochondria that affects the site II-site III regions of the oxidative-phosphorylation system. The apparent lack of control of the phospholipase A2 and ATPase activities in mitochondria from ethanol-fed animals suggests that the membrane microenvironment of these enzymes has been altered such that they can exert their catabolic effects more readily under conditions of mild perturbation. The fatty acid analyses demonstrate that the observed alterations both in the energy-linked functions and in control of the phospholipase and ATPase are not mediated through changes in the acyl chain composition of bulk-phase phospholipids.
 ...
PMID:Effect of chronic ethanol administration on energy metabolism and phospholipase A2 activity in rat liver. 15 52

1. The calcium-dependent ATPase activity of phospholipase-A2-digested sarcoplasmic vesicles decreases concomitantly with the contents of residual lysophospholipids and fatty acids when increasing albumin concentrations are applied. 2. Delipidated albumin preferentially removes unsaturated fatty acids and lysophosphatidylcholine. A complete removal of the phospholipids by albumin does not occur. 3. The membrane-bound lysophospholipids were analysed with respect to type of phospholipid, plasmalogen content and fatty acid chains by means of thin-layer chromatography and gas chromatography. 4. While the fatty acid composition of the lysophospholipids is independent of the degree of delipidation, the composition of the residual free fatty acids is found to change with the albumin concentration. 5. Reactivation of the Ca2+-ATPase by oleate leads to reasonable activities at room temperature as long as a minimum of about 30 lysophospholipid molec-les per ATPase is left. The course of the residual Ca2+-ATPase activity with the degree of delipidation is related to the presence of unsaturated fatty acids. 6. No specific role of either sphingomyelin or the plasmalogens has been found.
 ...
PMID:Effects of phospholipase A2 and albumin on the calcium-dependent ATPase and the lipid composition of sarcoplasmic membranes. 15 39

Inactivation of (Na+ + K+)-ATPase of Yoshida sarcoma cells and beef brain microsomes by phospholipase A2 and a cytotoxin P6 from snake venom has been examined in relation to their activity to degrade phospholipids. Cytotoxin P6 which was most basic and devoid of phospholipase activity was most effective in inhibiting the (Na+ + K+)-ATPase of Yoshida sarcoma cells. Phospholipase A2 from Naja naja which was most active in degrading phospholipids was least effective in inhibiting (Na+ + K+)-ATPase in Yoshida sarcoma cells or in beef brain microsomes. Addition of trace amounts of cytotoxin P6 to the phospholipase considerably enhanced the inactivation of (Na+ + K+)-ATPase. The evidence suggests that the charge of the inhibitor protein and its specific structure play an important role in the inactivation of (Na+ + K+)-ATPase.
 ...
PMID:Influence of charge on the inactivation of membrane bound (Na+ + K+)-ATPase of Yoshida sarcoma cells by inhibitor proteins from cobra venom. 23 2

The development of typical protrusions in isolated hepatocytes after incubation with phalloidin was prevented by phospholipase A (from bee venom). When cells were preincubated with low concentrations of phospholipase A and the enzyme was removed by washing, the number of cells affected by 10 microgram phalloidin/ml was markedly reduced. If the pretreated cells were allowed to recover after removal of phospholipase, the sensitivity to phalloidin returned to nearly normal values. Transient treatment of hepatocytes with sublytic concentrations of phospholipase A did not destroy cell membranes, whereas 5-fold higher concentrations of the enzyme produced large protrusions quite different from those appearing during phalloidin poisoning. These findings suggest that phosphatides are needed for the recognition of phalloidin by liver cells. A series of marker enzymes were analysed in isolated plasma membranes from rat liver after treatment with phospholipase A. Changes in the activities of K+ Na+-ATPase and of p-nitrophenylphosphatase were observed. Other membranal enzymes were not markedly influenced. The inhibitory effect of phospholipase A on the phalloidin response is discussed in context of earlier findings suggesting an evident role of a membranal protein for the recognition of phalloidin.
 ...
PMID:Transient desensibilization of isolated hepatocytes against phalloidin by treatment with phospholipase A. 63 83

Na,K-ATPase has been isolated in purified membrane fragments from kidney tissue and crystallized by phospholipase treatment to obtain two-dimensional, membrane-bound protein crystals. Scanning force microscopy has been used to identify and analyze the topography of the membrane fragments. Specific patterns in accordance with electron microscopic images have been found. In biological material under physiological conditions the scanning force is a crucial parameter for the resulting image at high resolution.
 ...
PMID:Na,K-ATPase in crystalline form investigated by scanning force microscopy. 132 99

The microsomal Ca(2+)-ATPase inhibitor 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBuBHQ) induced bronchoconstriction and vasoconstriction in the isolated perfused and ventilated rat lung. These effects were accompanied by increased levels of thromboxane and prostacyclin in the effluent perfusate. The effect of tBuBHQ was inhibited by L-655,240, a thromboxane receptor antagonist, indicating thromboxane-A2-mediated bronchoconstriction and vasoconstriction. Accordingly, the cyclooxygenase inhibitor indomethacin largely blocked the effects of tBuBHQ. The involvement of a phospholipase in the generation of thromboxane A2(TXA2) was supported by dibucaine protection on tBuBHQ effects. The results from this study indicate that tBuBHQ, probably by inhibiting the microsomal Ca(2+)-ATPase, can trigger the arachidonic acid cascade leading to the formation of TXA2, which in turn causes bronchoconstriction and vasoconstriction in rat lung.
 ...
PMID:Vasoconstriction and bronchoconstriction induced by 2,5-di-(tert-butyl)1,4-benzohydroquinone, an endoplasmic reticular Ca2+-ATPase inhibitor, in isolated and perfused rat lung. 141 86


1 2 3 4 5 6 7 8 Next >>