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 arrival of the nerve impulse to the nerve endings leads to a series of events involving the entry of sodium and the exit of potassium. Restoration of ionic equilibria of sodium and potassium through the membrane is carried out by the sodium/potassium pump, that is the enzyme Na+,K(+)-ATPase. This is a particle-bound enzyme that concentrates in the nerve ending or synaptosomal membranes. The activity of Na+,K(+)-ATPase is essential for the maintenance of numerous reactions, as demonstrated in the isolated synaptosomes. This lends interest to the knowledge of the possible regulatory mechanisms of Na+,K(+)-ATPase activity in the synaptic region. The aim of this review is to summarize the results obtained in the author's laboratory, that refer to the effect of neurotransmitters and endogenous substances on Na+,K(+)-ATPase activity. Mention is also made of results in the field obtained in other laboratories. Evidence showing that brain Na+,K(+)-ATPase activity may be modified by certain neurotransmitters and insulin have been presented. The type of change produced by noradrenaline, dopamine, and serotonin on synaptosomal membrane Na+,K(+)-ATPase was found to depend on the presence or absence of a soluble brain fraction. The soluble brain fraction itself was able to stimulate or inhibit the enzyme, an effect that was dependent in turn on the time elapsed between preparation and use of the fraction. The filtration of soluble brain fraction through Sephadex G-50 allowed the separation of two active subfractions: peaks I and II. Peak I increased Na+,K(+)- and Mg(2+)-ATPases, and peak II inhibited Na+,K(+)-ATPase. Other membrane enzymes such as acetylcholinesterase and 5'-nucleotidase were unchanged by peaks I or II. In normotensive anesthetized rats, water and sodium excretion were not modified by peak I but were increased by peak II, thus resembling ouabain effects. 3H-ouabain binding was unchanged by peak I but decreased by peak II in some areas of the CNS assayed by quantitative autoradiography and in synaptosomal membranes assayed by a filtration technique. The effects of peak I and II on Na+,K(+)-ATPase were reversed by catecholamines. The extent of Na+,K(+)-ATPase inhibition by peak II was dependent on K+ concentration, thus suggesting an interference with the K+ site of the enzyme. Peak II was able to induce the release of neurotransmitter stored in the synaptic vesicles in a way similar to ouabain. Taking into account that peak II inhibits only Na+,N(+)-ATPase, increases diuresis and natriuresis, blocks high affinity 3H-ouabain binding, and induces neurotransmitter release, it is suggested that it contains an ouabain-like substance.
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PMID:In search of synaptosomal Na+,K(+)-ATPase regulators. 136 48

The effect of various dietary fats on membrane lipid composition, fatty acid profiles and membrane-bound enzyme activities of rat cardiac sarcolemma was assessed. Four groups of male weanling Charles Foster Young rats were fed diets containing 20% of groundnut, coconut, safflower or mustard oil for 16 weeks. Cardiac sarcolemma was prepared from each group and the activities of Na+, K(+)-ATPase, 5'-nucleotidase, Ca(2+)-ATPase and acetylcholinesterase were examined. ATPase activities were similar in all groups except the one fed coconut oil, which had the highest activities. Acetylcholinesterase activity was also similar in all the groups, however, it was significantly higher in the group fed mustard oil. No significant changes were observed among the groups in 5'-nucleotidase activity, in the cholesterol-to-phospholipid molar ratio and in sialic acid content. The coconut, safflower and mustard oil diets significantly increased cholesterol and phospholipid contents and the lipid-to-protein ratio of cardiac sarcolemma as compared to feeding the groundnut oil diet. The fatty acid composition of membrane lipids was quite different among the various groups, reflecting the type of dietary fat given. The total unsaturated-to-saturated fatty acid ratio was not different among the various groups; however, the levels of some major fatty acids such as palmitic (16:0), oleic (18:1) and linoleic (18:2) acids were significantly different. Cardiac sarcolemma of the group fed safflower oil had the highest polyunsaturated fatty acid content. The results suggest that dietary fats induce changes not only in the fatty acid composition of the component lipids but also in the activities of sarcolemmal enzymes involved in the regulation of cardiac function.
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PMID:Effect of dietary fats on some membrane-bound enzyme activities, membrane lipid composition and fatty acid profiles of rat heart sarcolemma. 140 62

The effects of toluene and n-hexane on rat synaptosomal membrane fluidity and the integral enzymes acetylcholinesterase (AChE) and ATPase were studied in vitro. The synaptosome membranes were isolated in Percoll and sucrose gradients. After adding toluene and n-hexane to the incubation mixture (37 degrees) in 2,4,6 and 8 mM concentrations, the fluidity changes were measured by the lateral pyrene diffusion method from Percoll-isolated membranes, and the ATPase and acetylcholinesterase activities were determined from both synaptosome isolations. Addition of toluene caused a linearly correlated increase of the synaptosomal membrane fluidity and a linear decrease of the AChE activity. The ATPase activity did not decrease linearly but dose-dependently. In contrast to the effects of toluene in vitro, addition of n-hexane in the same concentration range had no comparable influence on membrane fluidity nor on the activities of both integral enzymes despite its even higher lipid/water partition coefficient. Toluene increases synaptosomal membrane fluidity and at the same time inhibits the integral enzymes, probably by disturbing the lipid/protein interaction.
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PMID:Effects of toluene and n-hexane on rat synaptosomal membrane fluidity and integral enzyme activities. 144 47

Multinucleated skeletal muscle fibers are compartmentalized with respect to the expression and organization of several intracellular and cell surface proteins including acetylcholinesterase (AChE). Mosaic muscle fibers formed from homozygous myoblasts expressing two allelic variants of AChE preferentially translate and assemble the polypeptides in the vicinity of the nucleus encoding the mRNA (Rotundo, R. L. 1990. J. Cell Biol. 110:715-719). To determine whether the locally synthesized AChE molecules are targeted to specific regions of the myotube surface, primary quail myoblasts were mixed with mononucleated cells of the mouse muscle C2/C12 cell line and allowed to fuse, forming heterospecific mosaic myotubes. Cell surface enzyme was localized by immunofluorescence using an avian AChE-specific monoclonal antibody. HOECHST 33342 was used to distinguish between quail and mouse nuclei in myotubes. Over 80% of the quail nuclei exhibited clusters of cell surface AChE in mosaic quail-mouse myotubes, whereas only 4% of the mouse nuclei had adjacent quail AChE-positive regions of membrane, all of which were located next to a quail nucleus. In contrast, membrane proteins such as Na+/K+ ATPase, which are not restricted to specific regions of the myotube surface, are free to diffuse over the entire length of the fiber. These studies indicate that the AChE molecules expressed in multinucleated muscle fibers are preferentially transported and localized to regions of surface membrane overlying the nucleus of origin. This targeting could play an important role in establishing and maintaining specialized cell surface domains such as the neuromuscular and myotendinous junctions.
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PMID:Cell surface acetylcholinesterase molecules on multinucleated myotubes are clustered over the nucleus of origin. 146 54

Methyl isocyanate (MIC) interaction with the rabbit erythrocyte membrane increased the fluidity of the membrane and decreased the osmotic fragility of erythrocytes both in vitro and in vivo in rabbits intoxicated with MIC subcutaneously. MIC inhibited both acetylcholinesterase (AChE) and adenosine triphosphatase (ATPase) activities of erythrocytes dose-dependently in vitro, while in vivo a decreased trend in ATPase activity with unaltered AChE activity was observed. MIC also caused significant decrease in plasma sodium level with corresponding increase in potassium level in rabbits. The observed effects are due to MIC, per se, as the hydrolysis products of MIC, methylamine and N,N'-dimethylurea did not affect the erythrocyte fluidity and enzymes activities both in vitro and in vivo while they increased the osmotic fragility of erythrocytes in vivo in rabbits administered subcutaneously in equimolar concentration to MIC dosage. Inhibition of Na(+)-K(+)-dependent ATPase with altered permeability to cations and also probably water transport of plasma membrane due to MIC interaction are envisaged.
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PMID:Acute toxicity of methyl isocyanate in rabbit: in vitro and in vivo effects on rabbit erythrocyte membrane. 153 91

Resorcinolic lipids, amphiphilic compounds from cereal grains show strong effects upon the activity of membrane enzymes. The concentrations for 50% inhibition of erythrocyte membrane acetylcholinesterase were in the range of 18-90 microM and were dependent on the length of the aliphatic side chain of the homologue and on the modification of hydroxyl groups in the benzene ring. Sulfonation of OH groups resulted in a drastic decrease of the inhibitory potency. The effect of resorcinolic lipids on the activity of Ca2+(calmodulin)-ATPase was the opposite. Up to concentrations of 50 microM alk(en)ylresorcinols stimulated the activity of this enzyme and only slight inhibition (approx. 30%) was observed above 100 microM. The results suggest that the effect of resorcinolic lipids might depend on their ability to alter the bilayer properties. Most probably these compounds decrease the mobility of membrane phospholipid molecules.
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PMID:Modulation of the activities of membrane enzymes by cereal grain resorcinolic lipids. 161 Apr 78

Denervated fast-twitch rabbit muscles were progressively losing their fresh weight and the yield of sarcotubular protein was increasing. The activity of Ca(2+)-ATPase was affected but very slightly, the basal Mg(2+)-ATPase and the Mg(2+)-ATPase/Ca(2+)-ATPase ratio however increased together with a simultaneous depression of the membrane-bound acetylcholinesterase activity. We did not observe any differences in density properties of sarcotubular fractions between control and denervated muscle. However, a relative enrichment in SM and H fraction could be seen after denervation with small changes in the content of the Ca(2+)-pump protein, increased levels of calsequestrin and cholesterol, mostly in the heavy and the SM fraction. After denervation the binding sites for 3H-PN-200-110 did not show any changes in receptor affinity, but the number of putative Ca(2+)-channels increased twice along with a depression of 3H-ouabain binding sites. We suggest that the denervation of fast-twitch muscle leads to the hypertrophy of the junctional sarcoplasmic reticulum and the T-system. Changes in the cholesterol content, in the number of putative Ca(2+)-channels and in Na+, K(+)-ATPase can affect the muscle contraction.
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PMID:Effects of denervation on the contents of cholesterol and membrane systems involved in muscle contraction in rabbit fast-twitch sarcotubular system. 165 Jul 29

Alterations in erythrocyte plasma membrane properties (enzymatic activities and membrane fluidity) have been observed in patients affected by insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM). In order to verify whether these alterations are present also in gestational diabetes mellitus (GDM) we studied the plasma membranes obtained from two different cellular types (erythrocyte from both mother and cord blood and placenta syncytiothrophoblast cell) of 16 healthy pregnant women and 15 women affected by GDM. The following determinations were performed on the membrane preparations: Na+/K(+)-ATPase activity, acetyl-cholinesterase (AchE) activity, membrane fluidity and cholesterol:phospholipid ratio. We observed a reduction of both enzymatic activities and a decrease of membrane fluidity in maternal and cord blood erythrocytes and in syncytiotrophoblast plasma membranes in GDM pregnant women in comparison with controls. The cholesterol to phospholipid ratio was significantly lower in the erythrocyte membranes of women affected by GDM than in normal pregnant women, while it was increased in the cord blood erythrocyte membranes and in placental membranes in GDM in comparison with controls. The present study found, in GDM patients, a membrane alteration similar to the abnormality reported in IDDM and NIDDM (i.e. decreased Na+/K(+)-ATPase activity), while opposite modifications were observed with regard to other membrane activities and properties. The different membrane alterations observed in GDM with respect to IDDM and NIDDM might be linked to the different degree of metabolic control, on the contrary the reduced Na+/K(+)-ATPase activity might be a primary event in the pathogenesis of diabetes mellitus per se and might constitute a signal of high risk of developing the disease later in the women affected by GDM during pregnancy.
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PMID:Modifications induced by gestational diabetes mellitus on cellular membrane properties. 165 18

The orientation of the enzyme Mg(2+)-ATPase (EC 3.6.1.3) in the transverse tubule (TT) membranes of skeletal muscle was investigated using highly purified chicken and rabbit TT vesicles. The percentage of sealed vesicles present in these preparations averaged 88 and 78%, respectively, as calculated from the detergent-induced increase in ouabain-sensitive (Na+, K+)-ATPase activity, ATP-dependent ouabain binding, and lactate dehydrogenase activity (sarcoplasmic enzyme trapped in the TT vesicles). Sidedness of the sealed vesicles, estimated from latency of 5'-nucleotidase, acetylcholinesterase, and adenylate cyclase, was predominantly right-side out (69-76%, chicken TT and 62-70%, rabbit TT). In both chicken and rabbit native vesicles, high Mg(2+)-ATPase activity was detected by addition of ATP to the extravesicular medium; this activity was increased 14-12% by alamethicin pointing to the external localization of the active site. Furthermore, the enzymatic activity resulted partially inhibited by treatment of the chicken TT vesicles with proteinase K or p-hydroxymercuribenzoate. Concanavalin A stimulated 4-fold the chicken TT Mg(2+)-ATPase activity, an effect not potentiated by detergent permeabilization of the intact vesicles, indicating that lectin-binding sites were also solvent accessible. This stimulatory effect was not observed in native or permeabilized rabbit TT vesicles. From these results we conclude that the TT Mg(2+)-ATPase is an ectoenzyme with its nucleotide-hydrolyzing site and glycosylated regions facing the extracellular space. Inhibitors of ion-motive ATPases did not modify the enzyme activity, suggesting a different physiological role for the TT Mg(2+)-ATPase which may be involved in the regulation of muscle fiber functions affected by extracellular ATP levels.
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PMID:Transverse tubule Mg(2+)-ATPase of skeletal muscle. Evidence for extracellular orientation of the chicken and rabbit enzymes. 166 Apr 76

Chlorpromazine, an antipsychotic drug is found to inhibit Na+K(+)-ATPase, Ca(2+)-ATPase and acetylcholinesterase activities in the microsomal membranes of rat in vivo, when the drug is injected for certain periods of time. The inhibition seems to be due to the changes in fatty acid composition of lipid and microviscosity of the membranes. However, once the drug has been withdrawn, the enzyme activities are found to return to the normal level in three to five weeks, suggesting that the drug effect is reversible.
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PMID:The in vivo inhibition of transport enzyme activities in different organs of rat by chlorpromazine is reversible. 166 11


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