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:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The sonication of 30 S dynein obtained from Tetrahymena cilia induced dissociation into 14-S subunits, some of the enzyme still remaining as intact 30 S dynein and partially dissociated dynein (21 S) in a minor amount. It was demonstrated that the enzymatic properties of the 14 S subunit are quite similar to those of 30 S dynein except for the Ca2+:Mg2+ ratio. ATPase (EC 3.6.1.3) (ATP phosphohydrolase activity of the 14 S subunit was steadily enhanced by increasing concentrations of Mg2+. It was also activated by Ca2+ with an optimum at 6 mM but inhibited by a further increase in concentration. The Ca2+:Mg2+ ratio at 1 mM was about 0.62. 0.6 M KCl stimulated ATPase activity of the 14 S subunit two-fold. The Mg2+-ATPase had an optimum at pH 6.2 and revealed a high activity over pH 10. The Ca2+-ATPase showed two optima at pH 6.2 and 9.5. The Km for ATP was 10 muM. Only 10% of the 14 S subunit recombined with the outer fibers in the presence of Mg2+. The 14 S subunit was shown to have the same mobility as that of 30 S dynein on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
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PMID:Dissociation of Tetrahymena 30 S dynein into 14 S subunit by sonication. 24 8

Several analogs of lysolecithin were found to solubilize human erythrocyte ghosts comparably or even better than other detergents. Derivatives with aliphatic chains of 12 to 14 carbons were most effective. The phosphorylcholine detergents apparently possess low protein-denaturing properties, since they, for the first time, allowed the solubilization of enzymatically active acyl-CoA:lysolecithin acyltransferase from thymocyte plasma membranes. The solubilized enzyme was not sedimented at 177,000 x g for 60 min and penetrated into Sepharose 6B gels. Low detergent concentration resulted in a selective extraction of the acyltransferase (about 70%) as compared to alkaline phosphatase, nucleotide pyrophosphatase, gamma-glutamyltransferase or Mg2+-ATPase (30 to 40%). The selectivity was reflected in sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns of soluble and sedimentable membrane fractions; three bands of approximately 53, 84, and 94 x 10(3) daltons were enriched in the supernatants, whereas one band of about 68 x 10(3) daltons was concentrated in the pellet. The preferential extraction of acyltransferase may be related to particularly high affinity of lysolecithin analogs for this enzyme, which at higher concentrations was competitively inhibited by these detergents. The inhibitor constants ranged from 1400 micron for the C10 analog (ET-10-H) to 80 micron for the compound with 16 carbons (ET-16-H) per aliphatic chain.
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PMID:Detergent properties of water-soluble choline phosphatides. Selective solubilization of acyl-CoA:lysolecithin acyltransferase from thymocyte plasma membranes. 42 75

The luminal plasma membrane of calf urinary bladder epithelium (urothelium) has been isolated by a method designed to preserve enzymic activity as well as structural integrity. The yield was about 80 micrograms per calf bladder. Low levels of 5' nucleotidase, Mg2+-ATPase and (Na+ + K+)-ATPase activities were found in the luminal membrane fraction. Cerebroside was the major lipid present and dodecyl sulphate gel electrophoresis revealed a complex protein and glycoprotein composition in the whole membrane. A membrane fraction consisting of only the plaque areas was shown to have a simpler protein composition with major polypeptides of apparent Mr 12 000 and 22 000. These may associate to form a 30 000 apparent Mr complex which could represent the individual 'particles' of the dodecameric subunits seen by electron microscopy in the plaque regions.
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PMID:The isolation and analysis of the luminal plasma membrane of calf urinary bladder epithelium. 49 98

Human blood platelets are capable of removing Ca2+ from the cytoplasm by means of an active, ATP-dependent and cyclic AMP-stimulated transport system. Calcium-accumulating vesicles are obtained by sonicating platelets. On density gradient centrifugation, this activity is found in the heavier of two membrane fractions. Concentrated in this fraction are also the Ca2+-stimulated Mg2+-ATPase and glucose-6-phosphatase, believed to be a marker for internal membrane systems. When the isolated vesicles are loaded with Ca2+, a third band separates from the two vesicular fractions in the density gradient. This band C contains virtually all the Ca2+-accumulating activity. Evidence that this activity is due to an active uptake and not to surface binding or adsorption is presented. Whereas electron microscopy does not reveal striking differences between active and inactive fractions, differences in protein composition are revealed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Furthermore, this band contains an enzyme system which converts arachidonic acid to malondialdehyde and therefore this fraction must be the site of prostaglandin synthesis. Membranes prepared by loading platelets with glycerol, followed by osmotic lysis are unable to accumulate calcium. In sodium dodecyl sulphate-polyacrylamide gel electrophoresis such membranes show significant differences in their protein pattern as compared to the actively Ca2+-accumulating vesicular membranes of band C. All preparations with Ca2+-accumulating activity also contain markers for plasma membranes and the question whether this activity is due exclusively to an intracellular structural element equivalent to the sarcoplasmic reticulum of muscle or whether an "extrusion pump" expelling Ca2+ to the outside of the cell is also involved, cannot yet be ;nswered.
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PMID:Further characterization of calcium-accumulating vesicles from human blood platelets. 69 5

Taurocholate transport was characterized in basolateral plasma membrane vesicles prepared from the livers of 14-day-old Sprague-Dawley rats using a self-generating Percoll gradient method. Liver plasma membrane protein yield, intravesicular volume, and enrichments of various marker enzymes were similar to those obtained for vesicles from adult rat liver. The basolateral marker enzyme Na+-K+-ATPase was enriched 26-fold in the suckling rat basolateral membrane fraction while the bile canalicular marker enzymes alkaline phosphatase and Mg2+-ATPase were enriched only 3- and 5-fold, respectively. The activities of marker enzymes for endoplasmic reticulum, mitochondria, or lysosomes were not enriched compared with homogenate. In the presence of an inwardly directed 100 mM Na+ gradient, vesicle accumulation of taurocholate transiently reached a concentration 1.5- to 2-fold higher than that at equilibrium ("overshoot") in suckling and adult membrane vesicles, but the initial rate of taurocholate entry and peak intravesicular accumulation were markedly decreased in suckling compared with adult membrane vesicles. In the presence of an inwardly directed 100 mM K+ gradient, the rate of uptake was slower, and no overshoot occurred in either suckling or adult rat vesicles. The decreased rate of Na+-coupled taurocholate uptake by membrane vesicles from suckling rat liver could not be explained on the basis of more rapid dissipation of the transmembrane Na+ gradient. Kinetic studies demonstrated saturable, Na+-dependent taurocholate uptake for both suckling and adult vesicles. However, the Vmax for taurocholate uptake in suckling rat vesicles was less than half of the adult rate (2.46 +/- 0.13 vs. 5.25 +/- 0.22 nmol X mg prot-1 X min-1, respectively, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Taurocholate transport by basolateral plasma membrane vesicles isolated from developing rat liver. 240 82

The relation between the rates of ATP-dependent Ca2+ uptake and ATP hydrolysis was studied in homogenates of eggshell gland mucosa and its subcellular fractions from the domestic fowl and duck. The Ca2+-Mg2+-ATPase activity was 5-10% of that of the "basal" Mg2+-ATPase at an optimal Ca2+ concentration in the subfractions. The presence of K+ and/or Na+ increased the rate of Ca2+ uptake and the Ca2+-Mg2+-ATPase activity; the effects of K+-Na+ were not inhibited by ouabain. The Ca/P ratio varied with the experimental conditions. At 10(-4) M Ca2+ and in the absence of K+ Na+ it was 0.8, and in their presence 0.4.
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PMID:Relation between Ca2+ uptake and ATPase activity in the particulate fractions of the eggshell gland mucosa of the domestic fowl and duck. 241 69

The status of Na+ regulation was examined during early stages of alkylation insult to rat liver. Na+/K+-ATPase activity in plasma membranes declined by 52% within 3 hr of treatment with 850 mg/kg acetaminophen. This loss preceded the release of alanine aminotransferase (2880 +/- 1550 U/ml) and necrosis (2+) seen at 24 hr. Activities of 5'-nucleotidase and Mg2+-ATPase and recovery of plasma membranes were comparatively unchanged at 3 hr. Because damage to Na+/K+-ATPase appeared early in the pathogenesis of acetaminophen hepatotoxicity, loss of hepatocellular Na+ regulation could represent one of the critical molecular consequences of lethal alkylation by acetaminophen.
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PMID:Early inhibition of the Na+/K+-ATPase ion pump during acetaminophen-induced hepatotoxicity in rat. 244 17

We have previously reported that Na+,K+-ATPase of nerve ending membranes is stimulated by catecholamines only in the presence of a brain soluble fraction. The filtration of this soluble fraction through Sephadex G-50 permitted the separation of two extracts of maximal UV absorbance (peaks I and II) which showed different effects on ATPases. Peak I stimulated both Na+, K+-ATPase and Mg2+-ATPase activities and peak II inhibited Na+, K+-ATPase activity. We have now studied the activity of ATPases in the presence of the whole eluate obtained from the Sephadex G-50 column. It was observed that maximal effects on ATPases were obtained with peaks I and II. Peak I and peak II fractions were unable to modify the activity of acetylcholinesterase or 5'-nucleotidase present in the synaptosomal membranes. The stimulatory effect of peak I on ATPases was concentration dependent (up to 1:100), it was stable at different pHs and it was reverted by catecholamines. The inhibitory effect of peak II on Na+,K+-ATPase was concentration dependent (up to 1:50,000), it was stable only at acid pH, and it was partially reverted by catecholamines. These findings indicate that the factors responsible for the effects of peaks I and II have different properties and that their actions on ATPases show enzyme specificity.
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PMID:Different properties of two brain extracts separated in Sephadex G-50 that modify synaptosomal ATPase activities. 245 36

Ouabain inhibited 86RbCl uptake by 80% in rabbit gastric superficial epithelial cells (SEC), revealing the presence of a functional Na+,K+-ATPase [(Na+ + K+)-transporting ATPase] pump. Intact SEC were used to study the ouabain-sensitive Na+,K+-ATPase and K+-pNPPase (K+-stimulated p-nitrophenyl phosphatase) activities before and after lysis. Intact SEC showed no Na+,K+-ATPase and insignificant Mg2+-ATPase activity. However, appreciable K+-pNPPase activity sensitive to ouabain inhibition was demonstrated by localizing its activity to the cell-surface exterior. The lysed SEC, on the other hand, demonstrated both ouabain-sensitive Na+,K+-ATPase and K+-pNPPase activities. Thus the ATP-hydrolytic site of Na+,K+-ATPase faces exclusively the cytosol, whereas the associated K+-pNPPase is distributed equally across the plasma membrane. The study suggests that the cell-exterior-located K+-pNPPase can be used as a convenient and reliable 'in situ' marker for the functional Na+,K+-ATPase system of various isolated cells under noninvasive conditions.
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PMID:Half of the (Na+ + K+)-transporting-ATPase-associated K+-stimulated p-nitrophenyl phosphatase activity of gastric epithelial cells is exposed to the surface exterior. 245 13

Ruthenium red inhibited Ca2+-ATPase and ATP-independent Ca2+ binding with rat heart sarcolemma in a concentration dependent manner; significant effects were evident at 0.25 microM and higher concentrations. The apparent Ka for Ca2+-ATPase was 1.02 +/- 0.02 mM Ca2+ and 1.47 +/- 0.12 mM Ca2+ in the absence and presence of 2.5 microM ruthenium red, respectively; however, no change in the Vmax (41.2 +/- 1.6 mumol Pi/mg/h) was observed. Likewise, the affinity of Ca2+ for both low and high affinity Ca2+ binding sites in sarcolemma was decreased by ruthenium red. Sarcolemmal Na+-dependent Ca2+ uptake, ATP-dependent Ca2+ accumulation, Mg2+-ATPase and Na+,K+-ATPase activities were not affected by ruthenium red. In sarcoplasmic reticulum preparations, ruthenium red (0.25 to 25 microM) enhanced Ca2+ uptake without altering the Ca2+-stimulated ATPase activity. The observed increase in Ca2+ uptake appears to be due to the depressant effect of the dye on Ca2+ release from the sarcoplasmic reticulum. In mitochondrial preparations, ruthenium red (0.025 to 25 microM) showed a marked inhibitory effect on Ca2+ uptake activity whereas the Mg2+-ATPase activity was unaltered. In isolated rat hearts, 0.025 microM ruthenium red produced a slight negative inotropic effect, whereas 0.25 to 2.5 microM ruthenium red elicited a biphasic response both in terms of developed tension and resting tension. High concentrations of ruthenium red (12.5 to 25 microM) resulted in the development of contracture. Electron microscopic studies revealed the presence of ruthenium red in the myoplasm of hearts perfused for 15 to 30 mins with 2.5 to 5 microM dye.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of ruthenium red on rat heart subcellular calcium transport. 246 13


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