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)

Phosphate depletion (PD) causes impaired insulin secretion and metabolic derangements in pancreatic islets. We studied PD, pair-weighed (PW), and PD and PW rats treated with verapamil (PD-V and PW-V) to examine the mechanisms of these derangements. Cytosolic calcium ([Ca2+]i) in PD islets was higher than that in PW, PD-V, and PW-V islets, and the values in the latter three groups were not different. Both basal and stimulated ATP in PD islets were lower than those in PW, PW-V, or PD-V islets. The maximum velocity (Vmax) of Ca(2+)-ATPase and the Km and Vmax of Na+,K(+)-ATPase were reduced in PD islets. In both PD-V and PW-V, the Vmax of Ca(2+)-ATPase was higher than that in PD, but lower than that in PW. Both initial and second phases of insulin secretion by PD islets were lower than those by PW and PW-V islets. In PD-V rats, insulin secretion was greater than that in PD rats, but only the second phase was significantly higher. The data are consistent with either of the following possibilities: 1) PD causes a change in the permeability of islets, allowing increased entry of Ca2+ into them and a fall in ATP of islets; the latter would impair the activity of both ATPases, leading to reduced Ca2+ extrusion from islets and, hence, an elevation in their [Ca2+]i; or 2) the primary defect in PD is a reduction in the activities of ATPases of islets due to the fall in ATP secondary to phosphorus deficiency. The decreased Ca2+ extrusion that ensues, even in the face of normal Ca2+ entry, will result in high [Ca2+]i. In either of these scenarios the rise in [Ca2+]i would inhibit mitochondrial oxygen consumption and ATP production, further lowering the ATP content of the islets. The higher [Ca2+]i and low ATP of PD underlie the impaired insulin secretion. Verapamil, by blocking normal or augmented Ca2+ entry into the islets, mitigates or prevents the derangements in islet function and metabolism.
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PMID:Verapamil corrects abnormal metabolism of pancreatic islets and insulin secretion in phosphate depletion. 130 29

A rapid and automated assay for inhibitors of Na+, K(+)-ATPase was developed by determining the amount of inorganic phosphorus (Pi) released by Na+,K(+)-ATPase in a centrifugal analyzer. This method avoids long incubation, strong acids and centrifugation as in the conventional manual method. The coefficients of variation of intra- and inter-assay at ouabain concentration 0.5 mumol/L were 1.0 and 1.4%, respectively. The method is quick, reproducible and easy compared with current techniques.
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PMID:A rapid assay for the measurement of Na+,K(+)-ATPase inhibitors. 131 16

A Ca(2+)-dependent ATPase, purified from cardiac microsomal membranes by solubilization and chromatography, is identified as cardiac sarcoplasmic reticulum ATPase on the basis of its electrophoretic mobility and its trypsin digestion pattern. The ATPase (both in membranous and purified form) is stimulated by calmodulin, while the skeletal muscle ATPase is not. Rapid kinetic experiments demonstrate that the calmodulin stimulation is already present within the first enzyme cycle following the addition of ATP, and consists of an increased turnover of the phosphorylated enzyme intermediate. The calmodulin effect does not involve the phosphorylation of any protein other than the ATPase. Following the incubation of ATPase with [gamma-32P]ATP, even in conditions of calmodulin stimulation, radioactive phosphorus is found only on the ATPase electrophoretic band, corresponding to the phosphorylated enzyme intermediate. These observations, together with the results obtained for [125I]calmodulin binding to the ATPase, suggest that the stimulation in turnover produced by calmodulin on the ATPase is due to a direct effect on the enzyme. This may provide an independent regulation of the cardiac sarcoplasmic reticulum Ca(2+)-ATPase, in addition to the known regulation mediated by other accessory proteins.
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PMID:Effect of calmodulin on sarcoplasmic reticulum Ca(2+)-ATPase isolated from cardiac muscle. 138 34

Membrane fluidity and lipid composition influence the activity of a variety of membrane proteins. Decreased rates of hepatic ion clearance are associated with the neonatal period. We postulated that hepatic basolateral membranes derived from suckling animals might be less fluid than those from adult animals. Basolateral membrane vesicles were prepared from the livers of 1-week-old (SBLMV) and adult (ABLMV) rats by a Percoll gradient method. Na+/K(+)-ATPase activities were similar in the two groups. Double bond index, cholesterol and cholesterol/phosphorus ratios were significantly higher in SBLMV compared with ABLMV, while lipid phosphorus and relative percentages of phospholipid subclasses did not differ. Fluorescence anisotropy measured using diphenylhexatriene as well as 2-(9-anthroyloxy)stearate was significantly greater in SBLMV compared with ABLMV, while measurements made with 12-(9-anthroyloxy)stearate were similar in both age groups. Mean excited state lifetimes, lifetime distributions, and rotational correlation times were similar in both groups. These data suggest that hepatic basolateral membranes derived from suckling rats are less fluid than those from adult animals and further suggest that this difference may be due to increased cholesterol in hepatic basolateral membranes derived from suckling animals.
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PMID:Developmental changes in hepatic basolateral membrane lipid composition and fluidity. 139 Aug 65

The success of heart transplantation is limited by the negative correlation between the length of the cold ischemic storage period and the quality of functional recovery. We use 23Na, 31P NMR spectroscopy, and hemodynamic parameters to describe temperature-dependent changes in sodium influx and the concentration of phosphorus high-energy compounds during different storage periods. Perfusion with Krebs-Henseleit solutions containing Dy(TTHA)3- permitted discrimination of intra- and extracellular sodium during cold ischemic storage. The 23Na NMR visibilities under the acquisition and processing parameters used in our experiments were 40 +/- 4% for the intracellular compartment and 97 +/- 11% for the extracellular compartment. At 4 degrees C, the intracellular Na+ accumulation exceeded that observed at 15 and 22 degrees C. The ATP and PCr depletion rates were much lower at 4 degrees C and the left ventricular contractility was higher after longer periods of storage, as the storage temperature decreased. The intracellular Na+ concentration cannot serve as a marker for the postischemic recovery probability. The relative activity of the Na/K ATPase pumps is not correlated with the preservation success. However, intracellular sodium ion accumulation is a major factor in the time lag of the reperfusion recovery.
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PMID:Sodium ion transport in rat hearts during cold ischemic storage: 23Na and 31P NMR study. 146 Nov 25

Fast and slow K+ efflux components, independently regulated by angiotensin II (AII), have been identified in bovine adrenocortical cells. We have further investigated the role of potassium in the control of aldosterone synthesis in two ways. Firstly, isotopic tracers, in conjunction with channel modulators, have been used to study the interrelationship of K+ and Ca2+ in the control of AII-stimulated aldosterone synthesis. Secondly, electron probe X-ray microanalysis (EPXMA) was used to quantify potassium, sodium, chlorine and phosphorous in control and AII-stimulated cells. The effects of verapamil on 43K efflux were measured at two stages during AII stimulation. During the first ten minutes of treatment, when efflux via the fast component predominates, AII and verapamil both slowed efflux and their effects were additive. If verapamil was added later, at the time when efflux by the fast component appeared exhausted and the stimulatory effect of AII on the slow efflux component was apparent, it again slowed efflux. These data suggest that verapamil prevents calcium-gated K+ channels from opening by blocking Ca2+ channels. However, verapamil had no effect on AII-stimulated calcium efflux. In addition to blocking Ca2+ channels, verapamil may directly inhibit potassium efflux. EPXMA showed a bimodal distribution of potassium concentrations in control cells. However, in cells stimulated with AII for five minutes, the mean potassium content was less than in controls and was not bimodally distributed. Sodium content was increased by AII-treatment, chlorine was lowered and phosphorus remained unchanged. The data confirm previous observations that AII inhibits Na+/K+ ATPase activity.
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PMID:The role of potassium and other ions in the control of aldosterone synthesis. 165 31

The paper examines the relationship between the clinical manifestations of pyelonephritis and the functional activity of enzymes of cation transmembrane erythrocyte transport (Mg(2+)-, N(+)-K(+)-, Ca(2+)-ATPases). An individual analysis ascertained that the patients who showed a low Ca(2+)-ATPase activity had marked signs of inflammation in the body, as evidenced by ESR, seromucoid and fibrinogen concentrations. These patients had more significantly depressed immune defense mechanisms as reflected by the levels of immunoglobulins, T-lymphocytes, complement, the neutrophil phagocytosis, and urinary IgA concentrations). Variations were also found in examining the excretion of a number of metabolites. There was a substantial decrease in urea, creatinine, titrated acid, phosphorus excretions in patients with deficient Ca(2+)-ATPase activity than in those with its high activity. It was concluded that there was a relationship between some clinical manifestations of pyelonephritis and the functional activity of enzymes of cation transmembrane transport. To treat metabolic disorders, membrane-protective agents are recommended to include into combined therapy.
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PMID:[The enzyme function of cationic transmembrane transport and its relationship to the homeostatic indices of patients with chronic pyelonephritis]. 183 Apr 30

Hypophosphatemia revealed in patients with acute disorders of cerebral circulation was one of the causes of a decrease of the content of 2,3-DPG, ATP in red blood cells and of a reduction of Ca2(+)-ATPase activity in red blood cell membranes. In the given group of patients, hypophosphatemia was provoked by complete parenteral feeding, hypocapnia and by loss of phosphorus with urine and congestive gastrointestinal contents.
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PMID:[Causes, sequelae and possible ways of preventing hypophosphatemia in patients with cerebral ischemia]. 196 92

The ATPase activity of RecA protein was examined by monitoring the changes of NMR phosphorus signals of ATP, ADP and inorganic phosphate. The areas of phosphorus-31 NMR peaks from inorganic phosphate and ADP, which increased with time, and the signals from ATP, which decreased with time, were fitted by a linear least square method to obtain the initial rate constants. The rate constants were examined for dependence on RecA protein concentration, temperature and pH. This assay system is useful for testing extrinsic physico-chemical effects on ATPase activity; because only essential components are present in a confined system, and the rate constants can be measured with a single step.
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PMID:An in vitro kinetic assay of ATPase by phosphorus-31 NMR. 214

X-ray microanalysis has been used to characterize the enzyme activity hydrolyzing the ATP analogue 5'-adenylylimidodiphosphate (AMP-PNP) in taste bud cells. Rabbit foliate papillae fixed with paraformaldehyde and glutaraldehyde were incubated cytochemically with AMP-PNP as the substrate and lead ion as capture agent. The reaction product which appeared on the microvilli of taste bud cells was examined using an energy dispersive X-ray microanalyzer connected to an analytical electron microscope. The X-ray spectrum thus obtained was compared with that obtained from the product obtained from the demonstration of ATPase activity. Comparison of the phosphorus/lead ratios in the two products showed that twice as much phosphorus was released from an AMP-PNP molecule by the activity in question compared with that released from an ATP molecule by ATPase activity. This indicates that the enzyme hydrolyzes AMP-PNP into AMP and imidodiphosphate and that the enzyme is adenylate cyclase or ATP pyrophosphohydrolase, which possesses a similar hydrolytic property, but not ATPase or alkaline phosphatase, which hydrolyzes AMP-PNP into ADP-NH2 and orthophosphate. This paper provides an example of the use of X-ray microanalysis as a tool for enzyme distinction. The method is applicable to a variety of enzymes and tissues.
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PMID:Identification of 5'-adenylylimidodiphosphate-hydrolyzing enzyme activity in rabbit taste bud cells using X-ray microanalysis. 216 24


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