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)

The (Ca(2+)+Mg2+)-ATPase of the plasma membrane is activated by negatively charged phospholipids. The mechanism of this activation was investigated by studying the effect of negatively charged phospholipids on the steady-state phosphointermediate level and on the p-nitrophenylphosphatase activity. Both parameters were differentially affected by different acidic phospholipids. The level of phosphoprotein intermediate was not affected by phosphatidylserine (20% of total phospholipid), but it was increased by 60% by phosphatidylinositol 4-phosphate. Phosphatidylserine increased the p-nitrophenylphosphatase activity, whereas phosphatidylinositol 4-phosphate had no significant effect. It is suggested that phosphatidylinositol 4-phosphate mainly affects a reaction step which leads to accelerated formation of the phosphointermediate, whereas the action of phosphatidylserine would affect two reaction steps, one upstream and one downstream of the phosphointermediate.
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PMID:Stimulation of the catalytic cycle of the Ca2+ pump of porcine plasma-membranes by negatively charged phospholipids. 131 67

Vanadate-sensitive ATPase (115 kDa molecular weight) in adrenal chromaffin granules is an intrinsic membrane enzyme with its catalytic site located at the outer surface of the granules. Upon incubation with [gamma-32P]ATP, the purified ATPase formed an alkaline-labile phosphoenzyme intermediate, which was inhibited by vanadate but not by Na+ or K+. Ratio of ATPase or phosphatase activity and formation of phosphoenzyme intermediate was constant during purification after the first glycerol density gradient centrifugation. Phosphatidylserine specifically activated the enzyme about three-fold by increasing the Vmax value without changing the Km for ATP. Other phospholipids, including phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine, as well as lysophospholipids and detergents, had no effect. These results indicated that the vanadate-sensitive ATPase belongs to the P-type ATPases, which differ from known cation-translocating P-type ATPases.
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PMID:Vanadate-sensitive ATPase from chromaffin granule membranes formed a phosphoenzyme intermediate and was activated by phosphatidylserine. 183 31

We have recently reported the reconstitution of the clathrin-coated vesicle proton-translocating complex with liposomes prepared from ethanol-extracted crude bovine brain lipids. Reconstitution of proton pumping by the isolated proton ATPase has now been achieved with liposomes prepared from pure lipids. Optimal proton pumping, as assessed by ATP-generated acridine orange quenching and 32Pi-ATP exchange, is achieved with liposomes prepared from phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and cholesterol at a weight ratio of 40:26.5:7.5:26, and a lipid-to-protein weight ratio of 200:1. Under such conditions, the extent of decrease of ATP-generated acridine orange quenching is 150-fold greater than that of native clathrin-coated vesicles. Cholesterol is required to stabilize the proteoliposome. Phosphatidylserine, which is most effective in activating ATP-hydrolytic activity of the solubilized enzyme, is not obligatory for reconstitution of proton pumping.
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PMID:Lipid requirements for reconstitution of the proton-translocating complex of clathrin-coated vesicles. 287 29

We have recently described a mutant of Chinese hamster ovary cells, termed G.7.1, that contains a temperature-sensitive, conditionally lethal mutation resulting in defective vacuolar acidification (Marnell, M. H., Mathis, L. S., Stookey, M., Shia, S.-P., Stone, D.K., and Draper, R. K. (1984) J. Cell Biol. 99, 1907-1916). To further characterize the lesion, clathrin-coated vesicles were partially purified from wild type and G.7.1 cells, and the thermolabilities of vanadate and oligomycin-insensitive, N-ethylmaleimide-sensitive, H+-ATPase activity, 32Pi-ATPase exchange activity, and proton pumping were compared. All three parameters of H+ pump activity were markedly diminished by preincubation at 44 degrees C for vesicles harvested from the G.7.1 cells, but not for those from wild type cells. Phosphatidylserine did not protect against heat inactivation in vesicle fractions prepared from G.7.1 cells. The results suggest that the mutation responsible for defective acidification in G.7.1 cells is expressed at the level of the proton pump of organelles present in our clathrin-coated vesicle-enriched preparation.
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PMID:Thermolabile proton translocating ATPase and pump activities in a clathrin-coated vesicle fraction from an acidification defective Chinese hamster cell line. 288 29

Phosphatidylserine (PtdSer)-liposomes when incubated with synaptosomal plasma membranes (SPM) of dog brain, evoked a significant increase (approx 80%) of the Ca2+-stimulated ATPase activity with maximal effect achieved at around 0.7 mumol PtdSer/mg SPM protein. Higher concentrations of PtdSer led to inhibition of the enzyme activity with respect to the maximal percentage of stimulation. Treatment of SPM with EGTA, to minimize the presence of bound cytoplasmic activator calmodulin, resulted in a mixed mechanism of inhibition of the enzyme activity (Vmax was decreased and Km increased) as estimated by Lineweaver-Burk plots. Addition of exogenous calmodulin resulted in an increase of Vmax and in a restoration of Km to control value. Ca2+-stimulated ATPase activity, in EGTA-treated SPM, showed the same figure of changes at different concentrations of PtdSer-liposomes as those of the control, but the turning point was now located at higher PtdSer concentrations. The results suggest that Ca2+-stimulated ATPase activity of SPM is modulated by PtdSer and that calmodulin participates in these interactions, probably, by regulating the contact between the enzyme and Ca2+ ions.
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PMID:Phosphatidylserine and calmodulin effects on Ca2+-stimulated ATPase activity of dog brain synaptosomal plasma membranes. 293 82

1. A study has been made to see whether the ATPase of the Na pump is activated by phospholipids.2. Solubilization of a membrane-containing (microsomal) fraction from ox brain cortex with deoxycholate removed most or all of the ouabain-inhibited ATPase and p-nitrophenylphosphatase (pNPPase) activities. Addition of sonicated dispersions of crude commercial samples of phosphatidic acid, phosphatidylinositol or phosphatidylserine stimulated both enzymic activities, but neither phosphatidylcholine nor phosphatidylethanolamine affected them. After partial purification by chromatography, however, definite activation was demonstrated only with that component of crude samples which migrated like phosphatidylserine.3. The ATPase activity dependent on phosphatidylserine was eliminated by removal of Na and K or by addition of ouabain and was substantially inhibited by oligomycin. The corresponding component of pNPPase activity was partially inhibited by ouabain or by removal of most of the K, but was little affected by oligomycin. The phosphatidylserine-dependent enzyme(s) therefore exhibited properties characteristic of the ATPase of the Na pump.4. Phosphatidylserine dispersions similarly activated both the ATPase and the pNPPase of the particulate enzyme preparations, untreated with deoxycholate.5. The results suggest that the system for active transport of Na and K involves a complex unit of phosphatidylserine and the protein of the ATPase.
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PMID:The involvement of phosphatidylserine in adenosine triphosphatase activity of the sodium pump. 425 Jul 71

A N-ethylmaleimide-sensitive ATPase was extracted and partially purified from clathrin-coated vesicles of bovine brain. During purification the enzyme lost activity which was restored by a purified phospholipid fraction from brain. Phosphatidylserine, but no other commercial phospholipids tested, replaced the brain lipid fraction as activator. Particles depleted of the ATPase exhibited no H+ pump activity when reconstituted with brain phospholipids by the cholate dilution procedure. H+ pump activity was restored by incubating the reconstituted vesicles with the partially purified ATPase.
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PMID:Activation and partial purification of the ATPase of clathrin-coated vesicles and reconstitution of the proton pump. 614 41

Phosphatidylserine (PtdSer) incubated with synaptosomal plasma membranes (SPM) of dog brain is incorporated into SPM in proportion to its concentration in the incubation medium. Low PtdSer concentrations progressively activated the SPM-associated (Na+ + K+)-stimulated ATPase and acetylcholinesterase. Increasing the PtdSer concentration above that which maximally stimulated the enzyme activities effected a progressive inhibition with respect to maximal stimulation. Arrhenius plots of (Na+ + K+ + Mg2+)-dependent ATPase and 5'-nucleotidase revealed a clear break at 23-24 degrees C for both enzymes in SPM untreated with PtdSer (controls), whereas a linear relation was obtained for SPM treated with PtdSer. Changes in the allosteric properties of (Na+ + K+)-stimulated ATPase by fluoride (F-) and/or of 5'-nucleotidase by concanavalin A (i.e. changes of Hill coefficients) indicate that PtdSer increases the membrane fluidity. These results suggest that modifications of lipid-protein interactions in SPM induced by PtdSer may have implications in the physiological processes in the central nervous system.
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PMID:Influence of phosphatidylserine on (Na+ + K+)-stimulated ATPase and acetylcholinesterase activities of dog brain synaptosomal plasma membranes. 633 12

Phosphatidylserine synthesis as measured by the incorporation of [(3)H]serine into phosphatidylserine (PtdSer) through the serine-base exchange enzyme system (serine-BEES) is markedly inhibited in Jurkat cells treated with caffeine. The caffeine-induced inhibition was compared to that observed in cells treated with either CD3 mAb or thapsigargin. While CD3- and thapsigargin-induced inhibition was related to the release of Ca(2+) from the endoplasmic reticulum (ER), a process that deprives the serine-BEES of its major cofactor, caffeine modified PtdSer synthesis in the absence of decreased Ca(2+) content of ER. Using Jurkat clones differing by the expression of cell surface markers or protein tyrosine kinases implicated in the CD3/TCR signal transmission pathway, we have shown that CD3 mAb-induced inhibition of PtdSer synthesis necessitates the expression of both the CD3/TCR and the protein tyrosine phosphatase CD45 at the cell surface as well as the presence of p56(lck) and ZAP-70 protein tyrosine kinases. By contrast, thapsigargin, a blocker of the Ca(2+)-ATPase of the ER, known for its Ca(2+) releasing properties, inhibited PtdSer synthesis in all the Jurkat clones tested, indicating that this compound bypasses the CD3/TCR-induced signals. Despite its lack of effect on Ca(2+) release from ER and on protein tyrosine phosphorylations, caffeine inhibited PtdSer synthesis in all the Jurkat clones. The use of several cAMP-inducing drugs and of others xanthine derivatives indicated that caffeine modify PtdSer synthesis either by a direct action on the serine-BEES or by a modification of the structure of the phospholipids used as substrate by the enzyme.
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PMID:Regulation of phosphatidylserine synthesis in Jurkat T cell clones: caffeine bypasses CD3/TCR-induced protein tyrosine kinases and calcium signals. 1060 May 31

Phosphatidylserine (PS) was exposed at the surface of human umbilical vein endothelial cells (HUVECs) and cultured cell lines by agonists that increase cytosolic Ca(2+), and factors governing the adhesion of T cells to the treated cells were investigated. Thrombin, ionophore A23187 and the Ca(2+)-ATPase inhibitor 2, 5-di-tert-butyl-1,4-benzohydroquinone each induced a PS-dependent adhesion of Jurkat T cells. A23187, which was the most effective agonist in releasing PS-bearing microvesicles, was the least effective in inducing the PS-dependent adhesion of Jurkat cells. Treatment of ECV304 and EA.hy926 cells with EGTA, followed by a return to normal medium, resulted in an influx of Ca(2+) and an increase in adhering Jurkat cells. Oxidised low-density lipoprotein induced a procoagulant response in cultured ECV304 cells and increased the number of adhering Jurkat cells, but adhesion was not inhibited by pretreating ECV304 cells with annexin V. PS was not significantly exposed on untreated Jurkat cells, as determined by flow cytometry with annexin V-FITC. However, after adhesion to thrombin-treated ECV304 cells for 10 min followed by detachment in 1 mM EDTA, there was a marked exposure of PS on the Jurkat cells. Binding of annexin V-FITC to the detached cells was inhibited by pretreating them with unlabelled annexin V. Contact with thrombin-treated ECV304 cells thus induced the exposure of PS on Jurkat cells and, as Jurkat cells were unable to adhere to thrombin-treated ECV304 cells in the presence of EGTA, the adhesion of the two cell types may involve a Ca(2+) bridge between PS on both cell surfaces. The number of T cells from normal, human peripheral blood that adhered to ECV304 cells was not increased by treating the latter with thrombin. However, findings made with several T cell lines were generally, but not completely, consistent with the possibility that adhesion to surface PS on endothelial cells may be a feature of T cells that express both CD4(+) and CD8(+) antigens. Possible implications for PS-dependent adhesion of T cells to endothelial cells in metastasis, and early in atherogenesis, are discussed.
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PMID:Phosphatidylserine-dependent adhesion of T cells to endothelial cells. 1083 84


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