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)

In liposomes with reconstituted shark Na+,K(+)-ATPase an uncoupled Na(+)-efflux and a Na+/Na+ exchange can be induced on inside-out oriented pumps by the addition of external (cytoplasmic) Na+ and MgATP to liposomes that either do not contain Na+ (and other alkali cations), or include 130 mM Na+ internally (extracellular). Both modes of exchange are electrogenic and accompanied by a net hydrolysis of ATP. The coupling ratio of positive net charges translocated per ATP split is found to be close to 3:1 and 1:1, respectively, for the two modes of exchange reactions at pH 7.0. By addition of the hydrophobic anion tetraphenylboron (TPB-), which imposes a negative electrostatic membrane potential inside the lipid bilayer, the ATP hydrolysis accompanying uncoupled Na+ efflux is increased with increasing TPB- concentrations. Cholesterol which increases the inner positive dipole potential of the bilayer counteracted this activation by TPB- of uncoupled Na+ efflux. Using the structural analog tetraphenylphosphonium (TPP+), which elicits an inside positive membrane potential, ATP hydrolysis accompanying uncoupled Na(+)-efflux is decreased. The rate of dephosphorylation in the absence of extracellular alkali cations was affected in a similar manner, whereas the dephosphorylation in the presence of extracellular Na+ inducing Na+/Na+ exchange was unaffected by the hydrophobic ions. In both modes of exchange the phosphorylation reaction was independent of the presence of hydrophobic ions. The hydrophobic ions affected the apparent affinity for cytoplasmic Na+, indicating that binding of cytoplasmic Na+ may involve the migration of cations to binding sites through a shallow cytoplasmic access channel. The results are in accordance with the simple electrostatic model for charge translocation in which two negative charges in the cytoplasmic binding domain of the Na+,K(+)-ATPase co-migrate during cation transport.
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PMID:Hydrophobic ion interaction on Na+ activation and dephosphorylation of reconstituted Na+,K(+)-ATPase. 775 25

The effect of retinol deficiency and curcumin and turmeric feeding on brain microsomal Na(+)-K(+)ATPase activity was investigated. The brain Na(+)-K(+)ATPase activity registered an increase of 148.5% as compared to the control group. Upon treating retinol deficient rats with curcumin or turmeric, the abnormally elevated activity showed a decrease of 36.9 and 47.1%, respectively, when compared to the retinol deficient group. An increase in Vmax by 67% and Km by 66% for ATP was observed in the retinol deficient group. Curcumin or turmeric fed retinol-deficient groups reduced the Vmax by 25 and 33%, while Km was reduced by 25 and 31%, respectively, compared to the retinol deficient group. Arrhenius plot of Na(+)-K(+) ATPase showed a typical bi-phasic pattern in all the groups. Cholesterol:Phospholipid ratio showed a decrease in the retinol-deficient group by 67.8%, which showed a marked increase in curcumin or turmeric treated groups. Detergents could increase the Na(+)-K(+) ATPase activity more in the control group than in the retinol deficient groups. Curcumin or turmeric improved the detergent action on the enzyme. Subsequent freezing and thawing over a period of 30 min decreased the enzyme activity by 22.8% in the retinol deficient group compared to 15.9% decrease in the control group. Curcumin or turmeric treated groups showed a decrease in the enzyme activity by 22.0 and 19.2%, respectively, when compared to the zero time in each group. In the presence of concanavalin-A (Con-A) there was only 52.4% stimulation in the enzyme activity in retinol deficient groups, compared to 108.0% in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of retinol deficiency and curcumin or turmeric feeding on brain Na(+)-K+ adenosine triphosphatase activity. 784 84

In this study the relationship between sarcolemmal free cholesterol content and intracellular calcium ion concentration ([Ca2+]i) was explored. In cultured neonatal rat cardiomyocytes the cellular free cholesterol content was modulated by treatment with liposomes. Using cholesterol-rich or cholesterol-free liposomes, sarcolemmal free cholesterol content was raised or diminished, respectively. An increased sarcolemmal free cholesterol content resulted in a decreased sarcolemmal fluidity, whereas cholesterol depletion resulted in an increase in sarcolemmal fluidity. Cholesterol enrichment was associated with an increased [Ca2+]i, while cholesterol depletion resulted in a decreased [Ca2+]i. The membrane mobilizing agent 2-(2-methoxyethoxy)ethyl 8-(cis-2-c-octylcyclopropyl)-octanoate (A2C) caused an increase in sarcolemmal fluidity, and an increased [Ca2+]i. Thus, although sarcolemmal cholesterol depletion as well as A2C treatment increased sarcolemmal fluidity, their effects on [Ca2+]i are opposite. These results indicate that the effect of sarcolemmal free cholesterol content on [Ca2+]i is not mediated by sarcolemmal fluidity. The mechanisms responsible for the observed results are: (i) activated Ca2+ channels when the sarcolemma is enriched with cholesterol, (ii) most likely a stimulated Ca(2+)-ATPase activity when the sarcolemma is depleted of cholesterol, and (iii) inhibited Na+/Ca2+ exchanger activity when A2C is incorporated in the sarcolemma.
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PMID:The effect of sarcolemmal cholesterol content on intracellular calcium ion concentration in cultured cardiomyocytes. 805 87

Zinc, protein, cholesterol, phospholipids, alkaline phosphatase (AlPase), acid phosphatase (AcPase), adenosine-5-triphosphatase(ATPase) and histology were studied in testis of zinc-deficient mice. Zinc and protein decreased in the 3-week experiment whereas they increased in the 6-week experiment. Zinc is involved in several functions of the cell and is regulated by hormones. Inhibition of spermatogenesis indicates for decreased zinc levels in 3-week whereas the increase in 6-week experiment indicates for accumulation of zinc in oedomatous fluid and uncontrolled diffusion of zinc across the blood testis barrier. Glycogen decreased in the 3-week as well as 6-week experiments due to blockage of androgen and spermatogenesis. Cholesterol and phospholipids increased in the 3-week experiment and decreased in 6-week experiment as both the parameters are related to steroidogenesis. Zinc deficiency leads to aspermatogenic condition and comparatively less injury to non-germinal cells. This could have blocked the transport of material across the testis barrier and therefore might have increased AlPase levels. Increased AcPase, probably represents lysosomal enzymes, as the cell debris of disorganised epithelium are to be digested and removed. ATPase increased in 3-week experiment and can be correlated to increased demands of energy of testicular cells to overcome the insults of zinc deficiency whereas the decrease in 6-week experiment could be as a result of inhibition of spermatogenesis.
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PMID:Histological and biochemical changes in testis of zinc deficient BALB/c strain of mice. 808 79

Cholesterol domains and transport have been well-studied in non-neuronal membranes in contrast to neuronal membranes. The purpose of the experiments reported in this paper was to determine: (1) exchangeable and non-exchangeable cholesterol domains or pools were present in brain synaptosomal membranes; (2) effects of hydrolysis of sphingomyelin on cholesterol pools, that has previously been shown to alter membrane cholesterol in non-neuronal membranes and; (3) sphingomyelin hydrolysis and enzyme activity. Cholesterol pools were determined using cholesterol exchange between radiolabeled small unilamellar vesicles and mouse synaptosomes. Activity of Ca(2+)+Mg(2+)-ATPase and Na(+)+K(+)-ATPase were measured in synaptosomal membranes following treatment with sphingomyelinase. The size of the exchangeable pool of synaptosomal membrane cholesterol was approx 50% of total membrane cholesterol when measured at 37 degrees C. The t1/2 of cholesterol exchange at 37 degrees C in synaptosomes was approx 10 h. Lowering the incubation temperature to 25 degrees C, significantly reduced the size of the exchangeable pool and significantly increased the t1/2 of cholesterol exchange. Sphingomyelinase treatment of synaptosomes significantly slowed cholesterol exchange but did not modify the size of the exchangeable pool of cholesterol. Ca(2+)+Mg(2+)-ATPase activity was significantly inhibited by sphingomyelinase treatment as compared to Na(+)+K(+)-ATPase activity. Cholesterol domains were described in neuronal tissue and the size and kinetics of those pools were altered by temperature-induced changes in fluidity and hydrolysis of sphingomyelin. Sphingomyelinase-induced changes in Ca(2+)+Mg(2+)-ATPase activity were not affected by hydrolysis of sphingomyelin but appeared to be associated with a reduction in cytofacial phosphatidylinositol.
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PMID:Kinetics and size of cholesterol lateral domains in synaptosomal membranes: modification by sphingomyelinase and effects on membrane enzyme activity. 839 83

Previous work has suggested that changes in nuclear membrane cholesterol may induce a stimulation in nuclear nucleoside triphosphatase (NTPase) activity. The purpose of the present study was to directly investigate if nuclear membrane cholesterol can stimulate nuclear NTPase activity. The cholesterol content of nuclei was altered with a liposomal methodology. The cholesterol content of nuclei isolated from hepatic tissue was relatively low in comparison to that typically exhibited by other membrane fractions. Because of this, it was difficult to further deplete the nuclear membrane of cholesterol, but we could successfully increase the cholesterol content after exposure to cholesterol-enriched liposomes. Nuclear NTPase activity was potently stimulated (approximately 150-200% of control) by an increase in the nuclear membrane cholesterol content. The Vmax of the NTPase activity in the presence of ATP or GTP was significantly increased after cholesterol enrichment without altering the affinity of the enzyme for these moieties. Mg2+ dependency of NTPase activity was also altered by cholesterol incorporation into the nuclear membrane. Cholesterol enrichment of the nuclear membrane also left the nuclei more susceptible to damage by salt-induced lysis than control nuclei. Our results clearly demonstrate that the cholesterol content of the nuclear membrane will have significant, direct effects on nuclear integrity and NTPase activity.
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PMID:Nuclear membrane cholesterol can modulate nuclear nucleoside triphosphatase activity. 897 60

The effect of chronic aluminium exposure (25 mg/kg b.wt.) was studied on the lipid composition and various membrane-bound enzymes in different regions of monkey brain. Aluminium (Al) administration caused a significant decrease in the total lipid, glycolipid, and phospholipid content of primate brain. Cholesterol levels and the phospholipid to cholesterol ratio were, however, markedly increased as a consequence of Al administration, thereby indicating a loss of membrane integrity. This was further confirmed when Al treatment was found to have a significant effect on the various membrane-bound enzymes in terms of decreased activities of Na+ K+ ATPase and acetylcholinesterase, along with a decrease in the activity of the myelin-specific enzyme, 2' 3'-cyclic nucleotide phosphohydrolase.
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PMID:Alterations in lipid composition and neuronal injury in primates following chronic aluminium exposure. 952 55

We have investigated the effects of cholesterol and omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexenoic acid (DHA) on Na, K-ATPase activity in human endothelial cells (HUVEC). Cultured HUVEC were incubated for 18 h with pure egg phosphatidylcholine (PC), or cholesterol-enriched liposomes (4 mg PC/ml). EPA and DHA alpha-tocopherol-acetate were emulsified with PC and incubated with HUVEC (10 mM). Na, K-ATPase and 5'-nucleotidase activities were determined using the coupled assay method on microsomal fractions obtained from cultured cells using non treated cells as control. Cholesterol enrichment significantly reduced both Na, K-ATPase and 5'-nucleotidase activities by a similar level (- 40%), whereas pure phospholipid liposomes inhibited this activity only by 22%. The dose-response curves of Na, K-ATPase activity were all biphasic assuming the presence of two independent sites exhibiting different affinities for ouabain of nM and microM respectively. The cholesterol induced inhibitory effect was greater for low affinity sites (-54%) as compared to that of the high affinity sites (-24%) whereas omega-3 fatty acids reduced the activity of both sites by 22%. Short term effects of EPA and DHA on Na, K-ATPase activity were determined by incubating microsomal fractions from untreated cells with various concentrations of free fatty acids (from 1 to 200 microM) for 20 min. Both EPA and DHA significantly reduced Na, K-ATPase activity but inhibition by EPA seems to be more effective than DHA. These results suggest that cholesterol and omega-3 fatty acids reduce Na, K-ATPase activity in HUVEC.
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PMID:Cholesterol and omega-3 fatty acids inhibit Na, K-ATPase activity in human endothelial cells. 1003 Mar 84

Ectopeptidases play important roles in cell activation, proliferation, and communication. Human monocytic cells express considerable amounts of aminopeptidase N/CD13, a transmembrane protein previously proposed to play a role in the regulation of neuropeptides and chemotactic mediators as well as in adhesion and cell-cell interactions. Here, we report for the first time that aminopeptidase N/CD13 in monocytes is partially localized in detergent-insoluble membrane microdomains enriched in cholesterol, glycolipids, and glycosylphosphoinositol-anchored proteins, referred to as "rafts." Raft fractions of monocytes were characterized by the presence of GM1 ganglioside as raft marker molecule and by the high level of tyrosine-phosphorylated proteins. Furthermore, similar to polarized cells, rafts in monocytic cells lack Na(+), K(+)-ATPase. Cholesterol depletion of monocytes by methyl-beta-cyclodextrin greatly reduces raft localization of aminopeptidase N/CD13 without affecting ala-p-nitroanilide cleaving activity of cells.
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PMID:Aminopeptidase N/CD13 is associated with raft membrane microdomains in monocytes. 1069 91

The aim of this study was to observe ethanol-induced membrane injury and to investigate the protective effect of betaine against chronic ethanol toxicity. Rats were divided into three groups: control group (n = 8), ethanol (8 g/kg per day) group (n = 8) and ethanol plus betaine (0.5% w/v) group (n = 8). Cholesterol concentrations (P < 0.05) and the cholesterol/phospholipid (C/PL) molar ratio (P < 0.01) were significantly increased in the erythrocyte membranes of ethanol-treated rats compared with those of the control group. Cholesterol (P < 0.05) and the C/PL ratio (P < 0.01) were decreased to control group levels after betaine administration. The activities of Ca(2+)-Mg2+ ATPase and Na(+)-K+ ATPase were lower than those of the control group (both P < 0.001), but the activities of these enzyme were increased in the betaine treatment group (P < 0.05). Our findings show that chronic ethanol consumption may affect membrane functions and betaine administration may be a useful agent for the treatment of chronic ethanol toxicity.
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PMID:Preventive effect of betaine on ethanol-induced membrane lipid composition and membrane ATPases. 1135 22


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