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)

Pig gastric microsomal (H+ + K+)-stimulated ATPase activity was nearly abolished within 10 min of digestion with phospholipase A2 at room temperature. The enzyme activity could be largely restored by a cytosolic activator protein partially purified from the gastric cells. The K+ sensitivity and turnover of 32P-labelled intermediates produced by the control and the activator-reconstituted microsomal (H+ + K+)-stimulated ATPase were closely similar but were widely different to those from treated membranes without activator reconstitution. The data suggest an essential requirement for the endogenous activator for gastric (H+ + K+)-stimulated ATPase function.
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PMID:Regulation of the gastric microsomal (H+ + K+)-transporting ATPase system by the endogenous activator. Effect of phospholipase A2 treatment. 630 57

Pig gastric microsomal vesicles enriched in gastric H+,K+-ATPase and K+-pNPPase were digested with bee venom phospholipase A2 at 21 or 37 degrees C. The unattacked phospholipids were then related to the remaining enzyme activities, followed by reconstitution with microsomal phospholipids and the endogenous activator protein. Gastric K+-stimulated ATPase was nearly abolished within 10 min of phospholipase A2 treatment. A substantial amount of pNPPase activity remained unaffected under identical conditions. About 80% of the microsomal phosphatidylethanolamine was attacked by phospholipase A2 at both temperatures while 60 and 79% of the phosphatidylcholine was hydrolyzed at 21 and 37 degrees C, respectively. Analysis of the phospholipids revealed that phospholipase A2 attacked only the phosphatidylcholine and phosphatidylethanolamine molecules enriched in polyunsaturated fatty acids. Microsomal H+,K+-ATPase system inactivated by phospholipase A2 at 21 degrees C could be largely restored by the endogenous activator alone. On the other hand, those inactivated at 37 degrees C needed pretreatment with phosphatidylcholine before assaying with the activator protein for maximal reconstitution; phosphatidylethanolamine was totally ineffective in restoration of the enzyme activity. Analysis of the fatty acid composition of the lysophosphatidylcholine following phospholipase A2 treatment at 21 and 37 degrees C suggested involvement of some phosphatidylcholine molecules relatively enriched in saturated fatty acids and extremely poor in polyunsaturated fatty acids in gastric ATPase function. The data not only pointed out the importance of phosphatidylcholine and the endogenous activator in gastric microsomal H+,K+-ATPase reaction but also demonstrated considerable heterogeneity within the same species of microsomal phospholipids.
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PMID:Effects of phospholipase A2 on gastric microsomal H+, K+-ATPase system: role of "boundary lipids" and the endogenous activator protein. 631 3

The total phospholipid content and distribution of phospholipid species between the outer and inner monolayers of the isolated sarcoplasmic reticulum membrane was measured by phospholipase A2 activities and neutron diffraction. Phospholipase measurements showed that specific phospholipid species were asymmetric in their distribution between the outer and inner monolayers of the sarcoplasmic reticulum lipid bilayer; phosphatidylcholine (PC) was distributed 48/52 +/- 2% between the outer and inner monolayer of the sarcoplasmic reticulum bilayer, 69% of the phosphatidyl-ethanolamine (PE) resided mainly in the outer monolayer of the bilayer, 85% of the phosphatidylserine (PS) and 88% of the phosphatidylinositol (PI) were localized predominantly in the inner monolayer. The total phospholipid distribution determined by these measurements was 48/52 +/- 2% for the outer/inner monolayer of the sarcoplasmic reticulum lipid bilayer. Sarcoplasmic reticulum phospholipids were biosynthetically deuterated and exchanged into isolated vesicles with both a specific lecithin and a general exchange protein. Neutron diffraction measurements directly provided lipid distribution profiles for both PC and the total lipid content in the intact sarcoplasmic reticulum membrane. The outer/inner monolayer distribution for PC was 47/53 +/- 1%, in agreement with phospholipase measurements, while that for the total lipid was 46/54 +/- 1%, similar to the phospholipase measurements. These neutron diffraction results regarding the sarcoplasmic reticulum membrane bilayer were used in model calculations for decomposing the electron-density profile structure (10 A resolution) of isolated sarcoplasmic reticulum previously determined by X-ray diffraction into structures for the separate membrane components. These structure studies showed that the protein profile structure within the membrane lipid bilayer was asymmetric, complementary to the asymmetric lipid structure. Thus, the total phospholipid asymmetry obtained by two independent methods was small but consistent with a complementary asymmetric protein structure, and may be related to the highly vectorial functional properties of the calcium pump ATPase protein in the sarcoplasmic reticulum membrane.
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PMID:Phospholipid asymmetry in the isolated sarcoplasmic reticulum membrane. 648 19

Mouse peritoneal macrophages have a phospholipase A2 activity which is optimally active at pH 8.5 (PLA8.5), requires 2 mM Ca2+ and is capable of hydrolyzing arachidonic acid from phosphatidylcholine and phosphatidylethanolamine. The specific activity of PLA8.5 can be greatly increased in macrophage sonicates by their incubation at 37 degrees C. This augmentation of PLA8.5 activity occurs maximally at pH 7.5, requires Ca2+, and is inhibited by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N',-tetraacetic acid and EDTA. The sulfhydryl-specific reagents N-ethylmaleimide and p-hydroxymercuribenzoate inhibit PLA8.5 activation but have no effect on the fully activated PLA8.5 enzyme itself. PLA8.5 activation is also augmented by ATP and is inhibited by pretreatment of the sonicates with ATPase and by beta-gamma-methylene ATP. The addition of the catalytic subunit of bovine heart cAMP-dependent protein kinase to macrophage sonicates in the presence of 1 mM reduced glutathione augments PLA8.5 activation. These data suggest that a protein kinase may be involved in the activation of PLA8.5 in mouse macrophage sonicates.
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PMID:Protein kinase activation of phospholipase A2 in sonicates of mouse peritoneal macrophages. 680 55

Stimulation of resident peritoneal macrophages resulted in release of arachidonic acid (AA) from phospholipids. This AA release is believed to occur as a result of the activation of phospholipases, usually by a phospholipase A2 (PLA2). The purpose of this study was to elucidate the role of cytosolic calcium ion concentration ([Ca2+]i) in the modulation of [3H]AA mobilization in peritoneal macrophages. [3H]AA release induced by ionophore A23187, opsonized zymosan, or 4 beta-phorbol 12-myristate acetate (PMA) occurred in the absence of extracellular calcium. Studies in fura-2/AM-loaded cells showed that zymosan and PMA did not increase [Ca2+]i significantly, whereas A23187 induced PLA2 activity translocation up to plasmatic membrane. Thapsigargin, an inhibitor of endomembrane Ca(2+)-ATPase, induced a rise in [Ca2+]i when cells were incubated in a Ca2+ medium. However, thapsigargin was not an effective stimulator of the translocation of PLA2 activity and [3H]AA release. These data indicate that changes in [Ca2+]i were not sufficient to elicit [3H]AA mobilization; this process seems tightly modulated by phosphorylation-dependent mechanisms in the presence of low [Ca2+]i.
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PMID:Influence of calcium on arachidonic acid mobilization by murine resident peritoneal macrophages. 748 85

Amphiphiles are known to modulate the activity of ATPase, phospholipase A2, adenylate and guanylate cyclase amongst others and relax vascular smooth muscle. The effect of two amphiphiles, lysophosphatidylcholine (LPC) and digitonin on the activity of nitric oxide synthase (NOS), as measured by conversion of radiolabeled L-arginine to L-citrulline, has been studied. Neither digitonin (0.01 mmol/l) nor LPC (0.01 mmol/l) influenced NOS activity in endothelial cell homogenates. Digitonin but not LPC stimulated NOS in intact endothelial cells. NOS activity was markedly inhibited by L- but not by D-omega-nitroarginine (D-NNA, 0.1 mmol/l). L-NNA or D-NNA data demonstrate no effect of amphiphiles on isolated NOS. NOS activation may occur as a result of detergent action on the membrane.
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PMID:Effect of amphiphiles on nitric oxide synthase in endothelial cells. 751 49

The amphiphile lysophosphatidylcholine (LPC) modulates the activity of membrane-associated enzymes such as phospholipase A2, adenylate and guanylate cyclases and ATPase. LPC also relaxes vascular smooth muscle through production of nitric oxide. On the basis of reports that bradykinin translocates nitric oxide synthase (NOS) from the membrane to the cytosol, we investigated whether a similar translocation occurs with LPC. It was found that LPC translocated NOS from the membrane to the cytosolic fraction. Total NOS activity remained at the control level.
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PMID:Intracellular translocation of endothelial nitric oxide synthase by lysophosphatidylcholine. 754 Jul 65

Myocardial ischemia in vivo is associated with dramatic electrophysiologic alterations which occur within minutes of cessation of coronary flow and are rapidly reversible with reperfusion. This suggests that subtle and reversible biochemical and/or ionic alterations within or near the sarcolemma may contribute to the electrophysiologic derangements. Our studies have concentrated on 2 amphipathic metabolites, long-chain acylcarnitines and lysophosphatidylcholine (LPC) which have been shown to increase rapidly in ischemic tissue in vivo and to elicit electrophysiologic derangements in normoxic tissue in vitro. Incorporation of these amphiphiles into the sarcolemma at concentrations of 1 to 2 mol%, elicits profound electrophysiologic derangements analogous to those observed in ischemic myocardium in vivo. LPC is produced in endothelial cells and myocytes in response to thrombin. Thus, activation of the coagulation system during ischemia may result in extracellular production and accumulation of LPC. The pathophysiological effects of the accumulation of both amphiphiles are thought to be mediated by alterations in the biophysical properties of the sarcolemmal membrane, although there is a possibility of a direct effect on ion channels. Inhibition of carnitine acyltransferase I in the ischemic cat heart was found to prevent the increase in both long-chain acylcarnitines and LPC and to significantly reduce the incidence of malignant arrhythmias including ventricular tachycardia and fibrillation. This review focuses on the influence of these amphiphiles on cardiac ionic currents observed during early ischemia and presents data supporting the concept that accumulation of these amphiphiles within the sarcolemma contributes to changes in ionic conductances leading to electrophysiological derangements. The contribution and the accumulation of these amphiphiles to alterations in intracellular Ca2+ as related to changes in Na/K-ATPase activity and intracellular Na+ are examined. Other alterations occur during early myocardial ischemia in addition to the events reviewed here; however, the results of multiple studies over the past 2 decades indicate that accumulation of these amphiphiles contributes importantly to arrhythmogenesis and that development of specific inhibitors of carnitine acyltransferase I or phospholipase A2 may be a promising therapeutic strategy to attenuate the incidence of lethal arrhythmias associated with ischemic heart disease in man.
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PMID:Selected metabolic alterations in the ischemic heart and their contributions to arrhythmogenesis. 754 31

As was shown in our previous work, the intracellular pH (pHi) of cultured human fibroblasts depends on cell density. The pHi is low in single cells, higher in cells, forming small groups and maximal in a sparse monolayer. On the other hand, the pHi is low in areas of confluent monolayers. In the present work, we show that the effects of inhibitors of various pH-controlling mechanisms as well as inhibitors of key enzymes in signal transduction pathways depend on the local cell density. We have found that N-ethylmaleimide and 7-chloro-4-nitrobenz-2-oxa-1,3-diazole, known as inhibitors of V-type H+ ATPase, inhibit the elevation of pHi induced by cell-cell contact interactions; meanwhile Cd2+ ions, which inhibit H+ conductive pathway, cause an increase of pHi in a confluent monolayer. Our data revealed also that the Na+/H+ antiporter does not play an essential role in the pHi regulation by intercellular contacts. Inhibitors of phospholipase A2 (4-bromophenacyl-bromide), phospholipase C (neomycin) and protein kinase C (H-7) dramatically change the way the pHi is modulated by local cell density. It is suggested that cell-cell interactions regulate cell activities via modulation of pHi, which is under positive control from phospholipase A2 and under negative control from protein kinase C.
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PMID:Regulation of intracellular pH by cell-cell adhesive interactions. 758 3

The importance of auxin as a signalling substance with hormonal character is well documented. Apart from various auxin-binding proteins described by several groups, little is known of downstream elements in the signal cascade triggered by auxin. A phospholipase A2 activated by auxin in vivo and in vitro was recently described by us. One of the auxin-binding proteins, a membrane-associated small glycoprotein, seems to participate in, or trigger, the auxin-activated phospholipase A2, since antibodies known to interact with this receptor interfere with the auxin activation. A second non-plant substance, the wasp peptide, mastoparan, was also used to demonstrate the participation of phospholipase A2 in auxin action. This peptide activates plant phospholipase A2 strongly and growth weakly. The weak growth activation may be due to inhibition of the plasma membrane H(+)-ATPase by mastoparan. Other downstream elements of the auxin signal transduction cascade postulated by us are lysophospholipids, which activate a membrane-associated protein kinase that may participate in the regulation of the plasma membrane H(+)-ATPase. One of the natural lysophospholipids in plants, lysophosphatidic acid, activates elongation growth and membrane-associated protein kinase. A continued search for further downstream elements of the auxin signal transduction cascade and improved knowledge of these elements should yield more tools to interfere with and dissect this signal transduction chain.
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PMID:Phospholipid signalling by phospholipase A2 in plants. The role of mastoparan and lysophospholipids as weak 'auxin-like' agonists. 759 46


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