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)

Axenically grown trophozoites of Entamoeba histolytica (NIH-200 strain) contain an active ATPase (170 nmol PO4/min per mg protein) with maximal activity at pH 8.8, a high affinity for ATP (Km approximately 40 micro M) and an absolute and specific requirement for Ca2+. The activation by Ca2+ shows positive cooperativity (nH = 2.48) at calcium concentrations below 8 micro M and no cooperativity between 8 and 25 micro M. The latter concentration fully saturates the enzyme. The observed activity is insensitive to oligomycin, ouabain and ruthenium red and is unaffected by a range of inhibitors of electron transport and uncouplers of oxidative phosphorylation. The enzyme exhibits structure bound latency and is tightly bound to cellular membranes. It is sedimentable ( greater than 80%) by high speed centrifugation of cell homogenates which are either protected osmotically or in which subcellular structures are damaged by sonication or treatment with Triton X-100. Arrhenius plots of V in the temperature range of 0-38 degrees C are linear without breaks, similar to other pyrophosphatases of E. histolytica. The calculated activation energy is 14.8 kcal/mol. This finding as well as the failure of phospholipase treatment to affect activity indicate that interactions with membrane lipids play no role in the catalytic function of this tightly membrane-bound ATPase.
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PMID:A calcium regulated adenosine triphosphatase in Entamoeba histolytica. 627 7

(1) The total phospholipid content of a gradient purified (K+ + H+)-ATPase preparation from pig gastric mucosa is 105 mumol per 100 mg protein, and consists of 29% sphingomyelin, 29% phosphatidylcholine, 28% phosphatidylethanolamine, 10% phosphatidylserine and 4% phosphatidylinositol. The cholesterol content corresponds to 50 mumol per 100 mg protein. (2) Treatment with phospholipase C (from Clostridium welchii and Bacillus cereus) results in an immediate decrease of the phosphate content. Up to 50% of the phospholipids are hydrolyzed by each phospholipase C preparation alone, without further hydrolysis by increased phospholipase concentration or prolonged incubation time. Combined treatment with the two phospholipase C preparations, sequentially or simultaneously, hydrolyzes up to 65% of the phospholipids. (3) The (K+ + H+)-ATPase and K+ stimulated p-nitrophenylphosphatase activities are decreased proportionally with the total phospholipid content, indicating that these enzyme activities are dependent on phospholipids. (4) Phospholipase C treatment does not change optimal pH, Km value for ATP and temperature dependence of the gastric (K+ + H+)-ATPase, but slightly decreases the Ka value for K+. (5) Phospholipase C treatment lowers the AdoPP[NH]P binding and phosphorylation capacities, suggesting that inactivation occurs primarily on the substrate binding level. (6) Most of the results can be understood by assuming that hydrolysis of the phospholipids by phospholipase C leads to aggregation of the membrane protein molecules and complete inactivation of the aggregated ATPase molecules.
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PMID:Studies on (K+ + H+)-ATPase. IV. Effects of phospholipase C treatment. 627 55

Ischemic injury was produced in the dog heart by occluding the left anterior descending coronary artery just below the second diagonal branch for a duration of 1.5 h followed by the release of occlusion. Nisoldipine, 3.5 micrograms/kg was injected intravenously 10 min before the occlusion and again 10 min before the commencement of reperfusion. The activity of serum creatine phosphokinase greatly increased after the reperfusion, and this increase was significantly suppressed by Nisoldipine. This drug, in addition, prevented ischemia-induced myocardial hemorrhage and premature ventricular contraction. Sarcolemmal membrane vesicles were prepared from an ischemic and non-ischemic portions of the myocardium 3 h after the commencement of reflow. The fraction was purified approximately 12-fold with respect to ouabain-sensitive (Na+K+)-ATPase as an indicator; contamination of mitochondria was minimum with cytochrome c oxidase as an indicator. Without treatment of Nisoldipine, the total amount of sarcolemmal phospholipid obtained from the ischemic area, as well as the amounts of phosphatidyl-choline and phosphatidyl-ethanolamine, were significantly decreased as compared with those obtained from the non-ischemic area. Nisoldipine treatment abolished the decrease in the sarcolemmal phospholipids, total as well as phosphatidyl-choline and -ethanolamine, induced by ischemia plus reperfusion. Therefore, our work indicates that the Ca++ channel antagonist, Nisoldipine, suppresses the ischemia-induced increase in phospholipid breakdown of cardiac sarcolemma probably through its inhibitory effect on the Ca++-mediated activation of membrane phospholipase, through its vasodilatory action, or both.
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PMID:The effect of a calcium channel antagonist, Nisoldipine, on the ischemia-induced change of canine sarcolemmal membrane. 631 Nov 55

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

Oral cholera vaccine contains 45% of O-antigen (serovars Ogawa and Inaba in equal parts) and at least 9 serologically active proteins; of these, toxoid (about 60% of the total amount of protein) and 5 enzymes have been identified: neuraminidase, proteinase, ribonuclease, phospholipase and ATPase. The safety, absence of reactogenicity and definite immunological effectiveness of the preparation in the primary immunization of volunteers have been shown.
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PMID:[Biochemical and immunochemical characteristics of a new oral, chemical cholera bivalent vaccine and results of a trial of the preparation on volunteers]. 676 Jun 28

The H(+)-ATPase from spinach chloroplasts was isolated and purified. Two-dimensional crystals were obtained from the protein/lipid/detergent micelles by treatment with phospholipase and simultaneous removal of detergent and fatty acids by Biobeads. The resulting two-dimensionally ordered arrays were investigated by electron cryomicroscopy. The ordered arrays showed top view projections of CF0F1. The images were analysed by correlation averaging. In this view CF0F1 has dimensions of 11.4 x 9 nm. The average view shows a strongly asymmetric molecule, in contrast to the rather hexagonal features of CF1, previously analyzed from two-dimensional arrays. It is concluded that this is due either to an asymmetric structure and positioning of CF0 relative to CF1 or to a rearrangement of CF1 subunits induced by binding of CF0 to CF1.
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PMID:Electron cryomicroscopy of two-dimensional crystals of the H(+)-ATPase from chloroplasts. 758 79

Although both alpha 1A- and alpha 1B-adrenoceptors are present in renal proximal tubules, the involvement of these receptor subtypes in the stimulation of Na+,K(+)-ATPase activity is not known. This study was undertaken to delineate the receptor subtype(s) involved in alpha 1-adrenoceptor-mediated increase in Na+,K(+)-ATPase activity and to identify the cellular signaling mechanisms such as stimulation of inositol triphosphate formation (IP3) and protein kinase C activation in this phenomenon. It was found that norepinephrine-induced increase in Na+,K(+)-ATPase activity was attenuated by prazosin, but not by rauwolscine, indicating the involvement of alpha 1-adrenoceptors. Furthermore, this response was selectively inhibited by the alpha 1B-adrenoceptor inactivator, chloroethylclonidine (100 microM), but not by the alpha 1A-adrenoceptor antagonist, WB4101 (0.01 microM). We examined whether these effects on Na+,K(+)-ATPase activity are mediated via the activation of IP3 and protein kinase C. Phenylephrine-induced increase in IP3 levels was abolished by prazosin, and significantly inhibited by WB4101, but not by chloroethylclonidine. Similarly, phenylephrine-induced activation of protein kinase C was sensitive to blockade by WB4101, but not by chloroethylclonidine. These results suggest that whereas both alpha 1A- and alpha 1B-adrenoceptors are present in proximal tubules, alpha 1B-adrenoceptors are involved in stimulating Na+,K(+)-ATPase activity and alpha 1A-adrenoceptors are predominantly linked to renal tubular IP3 production and protein kinase C activation. Therefore, it appears that norepinephrine-induced stimulation of Na+,K(+)-ATPase activity does not involve phospholipase-C-coupled protein kinase C pathway.
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PMID:Alpha 1-adrenoceptor subtypes mediating stimulation of Na+,K(+)-ATPase activity in rat renal proximal tubules. 772 Jul 75

It is known that mechanical stress directly changes the conformation of the functional proteins, or directly activates enzymes such as phospholipase in the plasma membrane. The integrin-cytoskeleton complex may be an alternative candidate structure for a mechanoreceptor and a transducer. The cytoskeleton has been also shown to play an important role in secretion. Mechanical stress may stimulate the secretion of some cytokines or angiotensin II, which may generate multiple intracellular signals as a secondary event. External stimuli are generally transduced into the nucleus through the activation of protein kinase cascade. Stretching of cardiac myocytes stimulates the activity of PKC, Raf-1 kinase, MAP kinase kinase. MAP kinase and S6 kinase. In cardiac myocytes, mechanical stress directly induces gene expression as well as protein synthesis. Immediate early genes are first induced, and then fetal-type genes are reinduced. Both in hypertrophied hearts and in the experimental model of cardiac hypertrophy induced by pressure overload. Ca(2+)-ATPase content of cardiac myocytes is depressed. Reduced function of sarcoplasmic reticulum causes insufficient decrease of intracellular calcium in diastole and induces slowing of ventricular relaxation. In the interstitium of pressure overloaded hearts, the accumulation of collagen fiber is increased. The abnormal deposit leads to increased chamber stiffness and diastolic dysfunction. Furthermore, TGF-beta and tissue renin-angiotensin system are up-regulated in pressure overloaded hearts, both of which accelerate the interstitial fibrosis.
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PMID:Interaction of cardiac myocytes and non-myocytes in mechanical stress-induced hypertrophy. 777 62

Several functions have been proposed for Rap1B in human platelets, including the regulation of phospholipase (PL) C gamma and Ca2+ ATPase. However, its localization is largely unknown. In the present study we have investigated the subcellular distribution of Rap1 by immunocytochemical techniques using affinity purified polyclonal antibodies raised against residues 121-137 common to the 95% homologous Rap1A and Rap1B proteins. By immunofluorescence, a positive labelling was obtained on intact resting platelets and was abolished after adsorption of the antibodies with the control peptide. Immunoelectron microscopy was then used to further define the subcellular localization of Rap1B in platelets and megakaryocytes (MK). In resting cells, immunolabelling for Rap1B was associated with the plasma membrane, mostly at its inner face, and lined the membrane of the open canalicular system (OCS). Some labelling was also found outlining the alpha-granules, identified as such by a double labelling with an anti-GPIIb-IIIa. On thrombasthenic platelets the same localization was observed. When platelets were stimulated by thrombin, immunolabelling for Rap1B was redistributed to the zones of fusion of the granules with the OCS, and to the plasma membrane with a higher concentration on pseudopods. Human MK expressed Rap1 and the staining revealed the association of the protein with the demarcation membranes and alpha-granules. This study presents a first approach to the localization of a small GTP binding-protein Rap1B in whole platelets and MK, and shows its association with both the plasma and OCS membranes, as well as with the alpha-granule membranes.
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PMID:Ultrastructural localization of the small GTP-binding protein Rap1 in human platelets and megakaryocytes. 780 84

Oxytocin stimulates phosphoinositide turnover in myometrium. To elucidate whether the coupling mechanism involves the interaction of oxytocin receptor with GTP-binding proteins, we examined oxytocin stimulation of guanosine triphosphatase (GTPase) activity and phospholipase-C activity in rat and human myometrial membranes. Oxytocin consistently stimulated both GTPase and phospholipase-C activities, and both stimulations were attenuated by an antibody directed against the carboxyl-terminals of the GTP-binding proteins, G alpha q and G alpha 11. Neutralization of the antibody by preincubation with antigenic peptide reversed this inhibition. [Thr4,Gly7]oxytocin, a specific oxytocin receptor agonist, stimulated both GTPase and phospholipase-C activities, and the stimulations were also inhibited by anti-G alpha q/11 IgG. Immunoreactive GTP-binding proteins, G alpha q and G alpha 11, and phospholipase-C beta 3 isoforms were present in myometrial membranes. These results indicate that stimulation of phospholipase-C activity by oxytocin in myometrium is mediated via G alpha q, G alpha 11, or a closely related GTP-binding protein, probably coupling to phospholipase-C beta.
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PMID:Oxytocin stimulates myometrial guanosine triphosphatase and phospholipase-C activities via coupling to G alpha q/11. 789 60


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