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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 stereochemical course of the phosphoric residue transfer from ADP to water catalyzed by the (Mg2+ + Ca2+)-dependent ATPase of sarcoplasmic reticulum has been determined. For this determination, the preparation is described of ATP gamma S, stereospecifically labeled in the gamma-position with both 17O and 18O. After hydrolysis of this nucleotide, the analysis of the product inorganic [16O,17O,18O]thiophosphate showed that the reaction proceeded with retention of configuration at the gamma-phosphorus atom. This result is expected since a phosphoenzyme is well characterized for this ATPase and provides support for the hypothesis that each phosphate transfer step occurs with inversion. In this case, the formation and breakdown of the phosphoenzyme occur each with inversion leading to the retention observed for the whole reaction.
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PMID:The stereochemical course of phosphoric residue transfer catalyzed by sarcoplasmic reticulum ATPase. 611 20

Phosphorus-31 saturation transfer NMR techniques have been employed to measure the unidirectional Pi consumption rate by respiration competent suspensions of the yeast Saccharomyces cerevisiae while the levels of ATP, ADP, and Pi are constant. These experiments are performed by saturating the ATP gamma phosphate resonance and observing the changes in the Pi resonance intensity while the yeast are respiring on endogenous substrates. The unidirectional Pi consumption rate is 3.5 +/- mumol s-1 (g of wet cells)-1. The rate is reduced 10-fold upon addition of oligomycin (80 micrograms/ML), suggesting that at least 90% of the Pi consumption activity is due to the mitochondrial F1-F0 ATPase. We have not been able to conclusively assign the remaining 10%. When the yeast are glycolyzing anaerobically, the unidirectional Pi consumption rate was 1.0 +/- 0.2 mumol s-1 (g of wet cells)-1. At most, 80% of this is due to Pi consumption by the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase leaving a residual activity of at least 0.2 mumol s-1 (g of wet cells)-1. Thus the activity in the oligomycin-inhibited cells under respiratory conditions and the nonglycolytic activity in anaerobic cells are equal to within the experimental errors. Furthermore the unidirectional rate of Pi consumption during anaerobic glycolysis is insensitive to oligomycin. These data suggest that the mitochondrial adenosinetriphosphatase is not turning over during anaerobic glycolysis. Possible explanations for this inhibition are discussed.
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PMID:In vivo phosphorus-31 nuclear magnetic resonance saturation transfer studies of adenosinetriphosphatase kinetics in Saccharomyces cerevisiae. 621 61

25-Hydroxyvitamin D3 1 alpha- and 24-hydroxylase, NADPH-cytochrome c reductase, heme oxygenase, and ATPase activities were studied in viable kidney cells isolated from rats submitted to unilateral kidney damage (cortical electrocoagulation) and during the development of acute renal failure subsequent to excision of the contralateral undamaged kidney. Measurements of blood pH, plasma total and ionized calcium, phosphorus, creatinine, kidney histology, and phosphorus nuclear magnetic resonance spectroscopy determinations of phosphorus-containing compounds in kidney tissue were also performed. Seventy-two hours after unilateral kidney damage, no significant changes were observed in blood pH or in the plasma parameters studied. During this period, a significant increase in the activity of the 25-hydroxyvitamin D3 hydroxylases could be demonstrated in the cells of the contralateral undamaged kidney. A similar pattern of compensatory rise in the activity of the other enzymes studied was not detected. However, in the damaged kidney viable cells, the hydroxylase activities remained unchanged relative to those in sham-operated controls, despite a 5-fold increase in the inorganic phosphate content and a marked decrease in the organophosphorus and ATP content of this tissue. During the development of acute renal failure, a significant decrease in the activity of the hydroxylases occurred only when the rise in plasma creatinine concentration suggested severe renal insufficiency.
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PMID:Changes in 25-hydroxyvitamin D3 alpha- and 24-hydroxylase activities of kidney cells isolated from rats with either unilateral kidney damage or acute renal insufficiency. 622 3

The change of subcellular phosphorus content in the liver was investigated after a single sc administration of synthetic [Asu1,7] eel calcitonin (CT) to fed rats. Administration of CT (80 MRC mU/100 g body weight) produced a significant increase in phosphorus content in the mitochondrial fraction, while this increase was not observed in fractions containing plasma membrane, nuclei, microsomes and cytosol. A significant increase in the mitochondrial phosphorus content was observed even at the lowest dose of CT (40 MRC mU/100 g body weight). A single ip administration of 2,4-dinitrophenol (0.1 mg/100 g body weight), an inhibitor of oxidative phosphorylation, did not prevent significant increases in phosphorus contents of the homogenate and the mitochondria caused by administration of CT (80 MRC mU/100 g body weight), although the drug markedly inhibited ATPase activity in the mitochondria. Administration of CT did not produce a significant alteration in the mictochondrial ATPase activity. These results suggest that phosphorus taken up by the liver cells after CT administration is largely located in the mitochondria, and that this increase is not related to oxidative phosphorylation. Presumably the hepatic mitochondria play a role in the storage of intracellular phosphorus increased by CT.
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PMID:Synthetic [Asu1,7] eel calcitonin increases phosphorus content in the hepatic mitochondria of rats. 622 93

The effects of modulators of Ca-ATPase and alkaline phosphatase (AP) activity on placental calcium and phosphorus transfer were studied using the in situ perfused guinea pig placenta. The diuretics ethacrynic acid and furosemide had no significant effect on placental calcium and phosphorus transfer when injected into the mother (1.0 or 10.0 mg X kg-1) or added to the solution perfusing the fetal side of the placenta (0.25 or 2.0 mM). These two drugs have previously been shown to inhibit placental Ca-ATPase and enhance AP activity in vitro. D-Penicillamine, which inhibits placental AP but not Ca-ATPase activity in vitro, also had no significant effect on net calcium and phosphorus transfer from mother to fetus either when given to the mother (50 mg X kg-1) or added to the placental perfusion solution (0.25 or 2.0 mM). These results suggest that placental transfer of calcium and phosphorus in the guinea pig may not be directly related to placental Ca-ATPase and AP activities.
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PMID:Placental calcium and phosphorus transfer in the guinea pig: lack of effect of modulators of Ca-ATPase and alkaline phosphatase activity. 622 20

Muscle ion composition, Na-K-ATPase activity, tissue respiration, and transmembrane potential differences were measured after 28 and 56 days of ethanol consumption (6.2 g X kg-1 X day-1) or an isocaloric amount of glucose in 12 and 4 dogs, respectively. Ethanol and glucose were given as supplements to an otherwise nutritious diet. After 28 and 56 days of alcohol consumption, skeletal muscle contents of phosphorus, magnesium, and potassium were significantly reduced as compared with either the control values or those in glucose-fed animals. In alcohol-fed animals, muscle sodium chloride, and calcium were significantly elevated. Ethanol consumption also resulted in hyperpolarization of the resting transmembrane potential of skeletal muscle fibers and a significant increase in Na-K-ATPase activity. No change was noted in Mg-ATPase activity. The increase in Na-K-ATPase activity was accompanied by increased sodium transport-dependent respiration. These results indicate that a subclinical myopathy may be induced by alcohol in the dog. Malnutrition did not appear to be a factor in this study, and thus the changes observed are believed to be due to ethanol per se. The magnitude and direction of these changes are similar to those observed in the skeletal muscle of chronically alcoholic humans. The changes in Na-K-ATPase activity and sodium transport-dependent respiration may represent adaptive responses of the muscle cell to ion transport or membrane disorders induced by ethanol.
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PMID:Derangements of muscle composition, ion transport, and oxygen consumption in chronically alcoholic dogs. 623 59

Phosphorus nuclear magnetic resonance spectra of sarcoplasmic reticulum membranes from rabbit muscle and of recombined membranes containing the calcium-dependent adenosinetriphosphatase (Ca-ATPase) of sarcoplasmic reticulum reveal two distinguishable, overlapping resonances. One resonance resembles a normal phospholipid bilayer resonance, and the other is much broader. The broader component is not seen in protein-free phospholipid vesicles. In recombined membranes of the Ca-ATPase, the intensity found in the broad component was proportional to the concentration of protein in the vesicles. The two-component spectra are interpreted to arise from at least two different domains of phospholipids, one of which is motionally restricted by the Ca-ATPase. Phospholipids exchange between these two domains at a rate less than 10(3) s-1. A model for protein-lipid interactions in membranes containing the Ca-ATPase is proposed in which some of the phospholipid head groups of the membrane interact directly with the protein.
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PMID:Two populations of phospholipids exist in sarcoplasmic reticulum and in recombined membranes containing Ca-ATPase. 623 19

Isolated myocytes were prepared from adult canine hearts using a combined technique of myocardial perfusion followed by incubation with collagenase. More than 60% of the cells routinely excluded trypan blue dye. Disruption of the myocytes was accomplished using high pressure nitrogen cavitation. After differential and sucrose gradient centrifugation, the peak sarcolemmal fraction averaged 100-fold enrichment in ouabain-inhibited K+-stimulated p-nitrophenyl phosphatase and 82-fold in ouabain-inhibited (Na+,K+)-ATPase. These sarcolemmal membranes are enriched in phospholipid phosphorus (1.98 mumol/mg of protein) and more than 4-fold in sphingomyelin and cholesterol. Polyacrylamide gels revealed three major protein peaks at 50,000, 91,000, and 140,000 apparent molecular weights. This work demonstrates the feasibility of preparing highly pure cardiac sarcolemma from isolated adult myocytes. The problem of cellular cross-contamination due to heterogeneity of cell types in whole myocardial tissue has been circumvented. The level of enrichment exceeds all reported preparations of cardiac sarcolemma from whole myocardium and cultured myocytes. This preparation should prove to be useful as an in vitro model for studies of physiological, pharmacological, and pathological perturbations of sarcolemmal structure and function.
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PMID:Preparation and properties of highly enriched cardiac sarcolemma from isolated adult myocytes. 624 86

The effect of cAMP-dependent protein kinases from rabbit skeletal muscles on Ca2+ uptake by fragments of skeletal muscle sarcoplasmic reticulum was studied. It was shown that incubation of the sarcoplasmic reticulum fragments with protein kinase increases the rate of Ca2+ uptake without changing the activity of Ca2+-dependent ATPase. This phenomenon is not accompanied by phosphorus incorporation into the protein components of the reticulum membranes. The protein kinase preparation subjected to "self-phosphorylation" is also capable to increase the rate of Ca2+ uptake. Using (14C) -oleic acid, it was shown that the increase of the rate of Ca2+ transport under effects of the "self-phosphorylated" protein kinase occurs due to the binding of free fatty acids present in the sarcoplasmic reticulum membranes. It was found that the effect observed is due to phosphofructokinase (ATP : D-fructose-6-phosphate-1-phosphotransferase) present in the protein kinase preparation.
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PMID:[Cause of increase in the efficiency of Ca2+ transport by fragments of sarcoplasmic reticulum from fast skeletal muscles induced by protein kinase]. 624 73

The content of adenine nucleotides, ATPase activity, the amount of total and inorganic phosphorus in the carp liver mitochondria were studied as affected by CO2 high concentrations. It is shown that during adaptation to the CO2 higher level in the medium the amount of ATP in fishes undergoes the most significant changes. The organism response to the effect of carbon dioxide depends on its concentration in the medium and time of its action. When fishes were for 24h under conditions of the 0.4mM CO2 concentration, the ATP content in the carp liver mitochondria surpasses the control level and under conditions the 0.8 mM CO2 concentration it reaches the control level. The presence of 0.4 and 0.8 mM CO2 concentration decreases the ATP content 7 days later. The amount of inorganic phosphorus in the liver mitochondria of experimental fishes undergoes similar changes. An increase in the CO2 concentration in the water medium up to 0,4 and 0,8 mM inhibits Na+, K+, Mg2+-ATPase in fish organelles, the inhibition being more pronounced in a trial with 0.8 mM CO2.
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PMID:[Peculiarities of phosphoric compound metabolism in liver mitochondria of carp adapted to higher concentrations of CO2 in water]. 624 95


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