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:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Arrhenius plots of a membrane (Na+ + K+)-dependent ATPase (adenosine triphosphatase) activity showed characteristic discontinuities, whereas those of the associated K+-dependent phosphatase activity did not. These findings support the contention that the phosphatase activity does not depend on phospholipid in the same way as does the ATPase activity.
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PMID:Differential effects of temperature on a membrane adenosine triphosphatase and associated phosphatase. 0 69

Plasma membrane from fusing embryonic muscle cells were assayed for phospholipase A activity to determine if this enzyme plays a role in cell fusion. The membranes were assayed under a variety of conditions with phosphatidylcholine as the substrate and no phospholipase A activity was found. The plasma membranes did contain a phosphatidic acid phosphatase which was optimally active in the presence of Triton X-100 and glycerol. The enzyme activity was constant from pH 5.2 to 7.0, and did not require divalent cations. Over 97% of the phosphatidic acid phosphatase activity was in the particulate fraction. The subcellular distribution of the phosphatidic acid phosphatase was the same as the distributions of the plasma membrane markers, (Na+ + k+)-ATPase and the acetylcholine receptor, which indicates that this phosphatase is located exclusively in the plasma membranes. There was no detectable difference in the phosphatidic acid phosphatase activities of plasma membranes from fusing and non-fusing cells.
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PMID:Phosphatidic acid phosphatase and phospholipdase A activities in plasma membranes from fusing muscle cells. 0 66

(Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) was purified from human cadaver renal tissue and exhibited a linear reaction rate with time. 100 g of whole kidney would yield 1--3.5 mg protein with a specific activity of 50--200 mol - kg-1 - h-1 for (Na+ + K+)-ATPase. The preparation was completely inhibited by 100 micronM ouabain with a Ki of 1.8 micronM. K+-dependent phosphatase increased during purification of (Na+ + K+)-ATPase to 7.8 mol - kg-1 - h-1. There was no detectable Mg2+-ATPase in the final preparation. Sodium dodecyl sulfate-polyacrylamide disc gel electrophoresis yielded three protein peaks of 117 000, 92 500, and 56 000 daltons. The peptide band corresponding to 92 500 daltons underwent an Na+-dependent phosphorylation with [gamma-32P]-ATP. The band at 56 000 daltons stained for glycoprotein. The Km for ATP was 0.38 mM and that for Mg2+ was 0.5 mM. The formation of ADP and inorganic phosphate from ATP was stoichiometric. The Km for Na+ in the presence of 20 mM K+ was 16 mM and the Km for K+ in the presence of 100 mM Na+ was 1.5 mM. The temperature optimum was 51degrees C and the pH optimum was 7.0. (Na+ + K+)-ATPase in whole homogenate, microsomes, and NaI-treated microsomes exhibited a slowing of reaction rate (non-linearity) with time such that the enzyme was inactive by 10--15 min of reaction. This non-linearity was eliminated during purification. The significance is discussed.
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PMID:Purification of the (Na+ + K+)-adenosine triphosphatase from human renal tissue. 1 1

Free-flow electrophoresis was used to subfractionate membrane vesicles from calf thymocyte plasma membranes. The fractionation resulted in a separation of vesicle populations bearing four different enzymes: alkaline nitrophenyl-phosphatase (orthophosphoric-monoester phosphohydrolase (alkalin optimum) EC 3.1.3.1), gamma-glutamyltransferase (EC 2.3.2.2), (Mg2+ + Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) and acyl-CoA:lysophosphatidylcholine acyltransferase (acyl-CoA:1-acylglycero-3-phosphocholine-O-acyltransferase, EC 2.3.1.23). The specific content of cholesterol and total phospholipid coincided with the distribution of membrane-bound protein. However, vesicles migrating towards the cathode had a higher molar ratio of cholesterol to phospholipid (0.75) compared to those migrating to the anode (0.55). Sodium dodecyl sulphate-gel electrophoresis of pooled vesicle fractions also demonstrates distinct differences in their protein pattern. Electron-micrographic thin sections show that the vesicle populations have a similar morphology and size distribution. These results are discussed in terms of heterogeneity of the original thymocytes, contamination with intracellular membranes and a heterogeneous structure of the plasma membrane.
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PMID:Fractionation of membrane vesicles. II. A method for separation of membrane vesicles bearing different enzymes by free-flow electrophoresis. 2 91

The localization of alkaline phosphatases in dentinogenically active rat incisor odontoblasts was studied by means of subcellular fractionation and electron microscopical histochemistry. Subcellular fractionation revealed the predominant phosphatase activity to be present in the microsome fraction and to a lesser extent in the mitochondrial fraction. Adenosine triphosphate degrading enzyme activity was determined in the presence or absence of (+/-)-6(m-bromophenyl)-5, 6-dihydroimidazo(le) (2,1-b) thiazole oxalate (R 8231). Before the histochemical study, the effects on phosphatase activities by aldehyde fixation were studied by biochemical assay. A method of fixation for optimal preservation of phosphatase activity is presented. Phosphatase electron microscopic histochemistry was performed by using ATP as a substrate and with or without addition of the inhibitor R 82319 Precipitates were seen in the membranes of vesicles present in the odontoblast process and the Golgi region. When there were signs of insufficient fixation, precipitates were also seen in the outer membranes of mitochondria. No phosphatase activity was seen in the cell membrane. ATP degrading enzyme activities mediated by nonspecific alkaline phosphatase (APase) and Ca2+ -adenosine triphosphatase thus have the same morphological localization. This close association is consistent with earlier biochemical studies.
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PMID:Ultrastructural localization of alkaline phosphatases in rat incisor odontoblasts. 2 17

Fresh peripheral blood lymphocytes from eight patients with congenital agammaglobulinemia demonstrate reduced ecto-5'-nucleotidase activity when compared to the mean activity of normal subjects and patients with other forms of immunoglobulin deficiency. A specific defect of ecto-5'-nucleotidase is further suggested by normal values for lymphocyte ecto-adenosinetriphosphatase and ecto-nonspecific phosphatase. The data provide evidence for an enzyme deficiency in this X-linked, B lymphocyte deficiency syndrome.
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PMID:Lymphocyte ecto-5'-nucleotidase deficiency in agammaglobulinemia. 2 64

This study examined the effects of vanadate on the potassium dependent phosphatase activity present in purified human kidney microsomal (Na+ + K+)-adenosine triphosphatase. Vanadate anion inhibited the K+-dependent phosphatase at a K1 of 35 nM. This inhibition was noncompetitive with the substrate, p-nitrophenylphosphate. The inhibition by vanadate at 1 mM K+ was only 45% of the inhibition that was observed at 10 mM K+. Neither preincubation of the enzyme with vanadate, nor changing the pH of the assay from 8.2 to 7.2 had any effect on the K1 for vanadate. The inclusion of 2.5 mM isoproterenol, to complex the yanadate, reversed the inhibition, as did diluting the enzymatic reaction. Vanadate also inhibited the overall (Na+ + K+)-ATPase reaction at a K1 of 1.91 microM. This inhibition was also reversible upon inclusion of isoproterenol in the assay. Increasing the level of magnesium from 6 mM to 30 mM lowered the K1 of vanadate to 0.25 microM. The possible role of vanadate as a physiological mediator of (Na+ + k+)-atpase activity is discussed.
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PMID:The effect of vanadate on human kidney potassium dependent phosphatase. 3 61

1) The rate of 2,3-bisphosphoglycerate breakdown is independent of pH value. 2) The adenine nucleotide pattern at alkaline pH values with its characteristic lowering of ATP and the accompanying accumulation of fructose-1,6-bisphosphate is caused by a relative excess of the activity of the hexokinase-phosphofructokinase system as compared wity pyruvate kinase. 3) The breakdown of adenine nucleotides proceeds via AMP mainly through phosphatase and not via AMP deaminase. 4) The constancy of the sum of nucleotides as long as glucose is present is postulated to be due to resynthesis via adenosine kinase which competes successfully with adenosine deaminase. 5) A procedure is given to calculate ATPase activity of glucose-depleted red cells. The results indicate that the ATPase activity is less at lower pH values and declines with time. An ATPase with a high Km for ATP is postulated. 6) During glucose depletion ATP production is mostly derived from the breakdown of 2,3-bisphosphoglycerate and the supply from the pentose phosphate pool both of which proceed at a constant rate. The contribution of pentose phosphate from the breakdown of adenine nucleotides amounts to 40% of the lactate formed at pH 6.8 and is about twice the lactate at pH 8.1.
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PMID:The breakdown of adenine nucleotides in glucose-depleted human red cells. 4 52

The sodium-potassium activated adenosine triphosphatase (NaKATPase) activity of the rat cornea was investigated histochemically using a Pb2+-precipitation technique in which adenosine triphosphate (ATP) is used as substrate and two methods for potassium-dependent para-nitrophenyl-phosphatase (K-NPPase) activity. With all the three techniques used it was demonstrated that the sodium-potassium-activated adenosine triphosphatase (NaK-ATPase) activity is localized in the cell membranes of the endothelium whereas a much weaker activity was observed in the epithelium. When the Pb2+-technique was used, the epithelial cell membranes showed a weaker reaction in the presence of ouabain. This activity was only Mg2+-dependent and was presumably due to an Mg2+-dependent ATPase. The validity of the histochemical techniques for NaK-ATPase activity is discussed. The results emphasize the importance of the endothelium as the main site of Na+ transport in the cornea. Small amounts of the enzyme are also present in the epithelium, which seems to be rich in Mg2+-ATPase. Provided that careful controls are performed, all the methods give consistent results in the cornea.
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PMID:Transport adenosine triphosphatase activity in the rat cornea. 6 3

The phosphorylation and dephosphorylation steps of the (Na-++K-+)-dependent ATPase (adenosine triphosphatase) (EC 3.6.1.3) reaction have been compared in 'normal', lipid-depleted and 'restored' membrane ATPase preparations. Partial lipid depletion was achieved by a single extraction with Lubrol W, and 'restoration' by adding pure phosphatidylserine. Gamma-32-P-labelled ATP was used for phosphorylation. The main findings were as follows. (1) Partial lipid depletion decreased but did not prevent Na-+-dependent phosphorylation, although it virtually abolished both Na-+-dependent and (Na-++K-+)-dependent ATPase activities. (2) 'Restoration' with phosphatidylserine produced an increment in phosphorylation that was the same in the presence and absence of added Na-+. (3) K-+ decreased the extent of Na-+-dependent phosphorylation of the depleted enzyme without producing a corresponding release of Pi. (4) K-+ rapidly decreased the extent of phosphorylation of the 'restored' enzyme to near-background value, with a concomitant release of Pi. (5) Na-+-dependent ATP hydrolysis was not restored. (6) The turnover of the 'restored' enzyme seemed to be higher than that of the 'normal' enzyme. The reaction sequence is discussed in relation to these results and the fact that the depleted enzyme retained about 50% of K-+-dependent phosphatase activity.
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PMID:Role of phospholipid in the intermediate steps of the sodium-plus-potassium ion-dependent adenosine triphosphatase reaction. 12 83


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