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)

Arrhenius plots of a membrane (Na+ + K+)-dependent ATPase (adenosine triphosphatase) activity showed characteristic discontinuities, whereas those of the associated K+-dependent phosphatase activity did not. These findings support the contention that the phosphatase activity does not depend on phospholipid in the same way as does the ATPase activity.
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PMID:Differential effects of temperature on a membrane adenosine triphosphatase and associated phosphatase. 0 69

The biochemical properties of the electrically excitable sodium channels in the electroplaque of Electrophorus electricus were investigated using tritiated tetrodotoxin (TTX) as a specific membrane probe. Membrane fragments from the electroplaque were isolated essentially by differential centrifugation and characterized with respect to the plasma membrane markers acetylcholine receptors, acetylcholinesterase, (Na+ + K+)ATPase, and [3H]TTX binding. Equilibrium binding studies showed that [3H]TTX bound to a single population of noninteracting receptor sites with an apparent dissociation constant of 6 +/- 1 X 10(-9) M. The toxin-membrane complex dissociated with a first-order rate constant of 0.012 sec-1. Studies on the pH dependence of complex formation demonstrated the requirement for an ionizable, functional group with a pK of 5.3 and this group has been shown to be a carboxyl. Treatment of the membranes with trimethyloxonium tetrafluoroborate, a carboxyl group modifying reagent, resulted in an irreversible loss in the binding of [3H]TTX, which could be prevented by low concentrations of TTX or saxitoxin. This decrease was due to a reduction in the total number of binding sites and not to a decrease in toxin binding affinities. The relative binding affinities of various monovalent alkali metal and polyatomic cations for the TTX-receptor site showed that this site displayed cation discrimination properties which were similar to those reported previously for the electrically excitable sodium channel in intact nerve fibers. A possible role for this site in the ion selectivity of the sodium channel is proposed.
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PMID:Properties of the tetrodotoxin binding component in plasma membranes isolated from Electrophorus electricus. 0 13

Active buffer transport, e.g. H+ -secretion by stomach and kidney and HCO3--secretion by pancreas and salivary glands, is linked with the presence of a HCO3-stimulated ATP-Phosphohydrolase. In contrast to (Na+ -k+)-ATPase which is considered to be equivalent to the Na+ pump, the HCO3--ATPase requires only one ion for activation and is insensitive to ouabain. The HCO3--ATPase is found in the plasma membrane of the epithelia, but in contrast to the (Na+ -k+)-ATPase it is located in the luminal cell border. The activity of the HCO3--ATPase changes in parallel along with the rate of active buffer transport, a finding which underlines its importance as a transport enzyme. Several disorders of buffer transport are described which are possibly associated with a defect of the HCO3--ATPase system.
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PMID:[The role of HCO3- ATPase in H+ /HCO3-Secretion (author's transl)]. 0 81

Plasma membrane from fusing embryonic muscle cells were assayed for phospholipase A activity to determine if this enzyme plays a role in cell fusion. The membranes were assayed under a variety of conditions with phosphatidylcholine as the substrate and no phospholipase A activity was found. The plasma membranes did contain a phosphatidic acid phosphatase which was optimally active in the presence of Triton X-100 and glycerol. The enzyme activity was constant from pH 5.2 to 7.0, and did not require divalent cations. Over 97% of the phosphatidic acid phosphatase activity was in the particulate fraction. The subcellular distribution of the phosphatidic acid phosphatase was the same as the distributions of the plasma membrane markers, (Na+ + k+)-ATPase and the acetylcholine receptor, which indicates that this phosphatase is located exclusively in the plasma membranes. There was no detectable difference in the phosphatidic acid phosphatase activities of plasma membranes from fusing and non-fusing cells.
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PMID:Phosphatidic acid phosphatase and phospholipdase A activities in plasma membranes from fusing muscle cells. 0 66

Two membrane fractions prepared from the Ehrlich ascites-tumor cell show non-identical stimulatory responses to certain amino acids in their Mg+2 -dependent activity to cleave ATP, despite the presence of ouabain and the absence of Na+ or K+. The first of these, previously described, shows little (Na+ + K+)-ATPase activity, and is characteristicallly stimulated by the presence of certain diamino acids with low pK2, and at pH values suggesting that the cationic forms of these amino acids are effective. The evidence indicates that these effects are not obtained through occupation of the kinetically discernible receptor site serving characteristically for the uphill transport of these amino acids into the Ehrlich cell. The second membrane preparation was purified with the goal of concentrating the (Na+ +K+)-ATPase activity. It also is stimulated by the model diamino acid, 4-amino-1-methylpiperidine-4-carboxylic acid, and several ordinary amino acids. The diamino acids were most effective at pH values where the neutral zwitterionic forms might be responsible. Among the optically active amino acids tested, the effects of ornithine and leucine were substantially stronger for the L than for the D isomers. The list of stimulatory amino acids again corresponds poorly to any single transport system, although the possibility was not excluded that stimulation might occur for both preparations by occupation of a membrane site which ordinarily is kinetically silent in the transport sequence. The high sensitivity to deoxycholate and to dicyclohexylcarbodiimide of the hydrolytic activity produced by the presence of L-ornithine and 4-amino-1-methyl-piperidine-4-carboxylic acid suggests that the stimulatory effect is not merely a general intensification of the background Mg+ -dependent hydrolytic activity.
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PMID:Amino acid stimulation of ATP cleavage by two Ehrlich cell membrane preparations in the presence of ouabain. 0 67

Sulphatide (cerebroside sulphate) metabolism of C3H/He mouse kidney was investigated in the course of compensatory renal hypertrophy in association with the change of [Na+,K+]-dependent ATPase, arylsulfatase A and beta-galactosidase activity. A remarkable increase in 35S incorporation into kidney sulphatide was observed 24 hours and especially 7 days after unilateral nephrectomy. In contrast, no significant alteration of 32P incorporation into major phospholipids such as phosphatidylcholine, phosphatidylethanolamine and sphingomyelin was demonstrated in the compensatory hypertrophied mouse kidney. [Na+, K+]-dependent ATPase increased to 126% of control in the remaining kidneys on 7 days after operation. Specific increase in 35S specific activity of kidney sulphatide suggests its possible link with the process of active ion transport through membrane-bound [Na+,K+]-dependent ATPase. Arylsulphatase A activity increased to 151% of control on days, while little change was observed in beta-galactosidase activity. These results suggest a sole concern of a turnover of sulphate moiety of sulphatide molecule in the elevated metabolism.
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PMID:Enhancement of sulphatide metabolism in the hypertrophied kidney of C3H/He mouse with reference to [Na+, K+]-dependent ATPase. 0 13

(1) The ATPase inhibitior protein has been isolated from rat liver mitochondria in purified form. The molecular weight determined by sodium dodecyl sulfate gel electrophoresis is approximately 9500, and the isoelectric point is 8.9. (2) The protein inhibits both the soluble ATPase and the particle-bound ATPase from rat liver mitochondria. It also inhibits ATPase activities of soluble F1, and inhibitor-depleted submitochondrial particles derived from bovine heart mitochondria. (3) On particle-bound ATPase the inhibitor has its maximal effect if incubated in the presence of Mg2+. ATP at slightly acidic pH. (4) The inhibitor has a minimal effect on Pi-ATP exchange activity in sonicated submitochondrial particles. However, unexpectedly the inhibitor greatly stimules Pi-ATP exchange activity in whole mitochondria while the low ATPase activity of the mitochondria is not affected. The possible mechanism of action of the inhibitor on intact mitochondria is offered.
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PMID:Purification and properties of ATPase inhibitor from rat liver mitochondria. 0 95

The teleostean gill is characterized by an exceptionally low permeability to water. Water moves along the osmotic gradient across the gill, being gained in fresh water and lost in sea water. Coupling of water movement to solute movement has not been reported. In fresh water, the gill is the site of independent active uptake of sodium and chloride. Na+ uptake is coupled to H+ or NH4+ excretion, Cl- uptake to HCO3- excretion. Amiloride blocks sodium transport and thiocyanate inhibits the chloride pump. In sea water, sodium and chloride exchanges across the gill are about 100 times faster than in fresh water, up to 100% of the internal sodium or chloride being exchanged per hour. Chloride is actively excreted, while sodium movement may well be passive. The chloride pump is associated with a mechanism for Na/K exchange; both pump and Na/K exchange are blocked by thiocyanate and possibly by ouabain. Three enzymes are involved in the ionic pumps: carbonate dehydratase (EC 4.2.1.1; carbonic anhydrase), sodium/potassium-stimulated adenosine-triphosphatase (EC 3.6.1.3, ATPase) and anion-stimulated ATPase. Specialized cells ('chloride cells') are presumably the site of the active transport.
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PMID:Transport of ions and water across the epithelium of fish gills. 0 38

Centrifugation of homogenates of bovine retinas to isopycnic equilibrium in sucrose density gradients yielded three partially overlapping bands of particles which were, in the order of increasing density: (a) photoreceptor cell (rod) outer segments; (b) plasma membranes, lysosomes, and large fragments of endoplasmic reticulum; and (c) mitochondria. The only enzyme activity investigated which had a peak coinciding only with outer segment fractions was guanylate cyclase. Enzyme activities with peaks in both the outer segment and denser fractions included 5'-nucleotidase and cyclic GMP phosphodiesterase. Enzyme activities with peaks only in the denser fractions included sodium and potassium ion-activated ATPase ((Na+ + K+)-ATPase), adenylate cyclase, cyclic AMP phosphodiesterase, beta-glucosidase, beta-galactosidase, and succinate-dependent cytochrome c reductase. These results suggest that some of the activities once thought to be present in rod outer segments are actually present in particles from elsewhere in the retina which contaminate rod outer segment preparations.
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PMID:Distribution of enzyme activities in subcellular fractions of bovine retina. 0 65

Slices of submaxillary gland were incubated in vitro in an enriched Krebs-Ringer-bicarbonate medium gassed with 95% O2-5% CO2 at 37 degrees C and the release of K+ into the medium was monitored after stimulation with alpha and beta adrenergic secretagogues under a variety of experimental conditions. K+ was released by the slice system after addition of norepinephrine, epinephrine or phenylephrine, but not after addition of isoproterenol. The extent of K+ release after norepinephrine depends on the dose of secretagogue and is higher when glucose, adenine and inosine, or all three substrates are absent from the medium. The effect of norepinephrine on K+ release is reversed by phentolamine but not by propranolol. Phentolamine also causes a 9.4-fold shift to the right in the dose-response curve to norepinephrine. Addition of ouabain to the incubation medium results in a higher extent of K+ release and prevents the reversal caused by phentolamine. The response to norepinephrine fails to occur when Ca++ is absent from the medium, either by chelation with ethylene glycol bis (beta-amino-ethyl ether)-N,N'-tetraacetic acid or by elimination from the Krebs-Ringer solution, and shows gradations depending on the Ca++ content of the medium. By itself, however, Ca++ does not induce K+ release from the slice system. The following conclusions are derived from these observations: 1) the release of K+ ions from the submaxillary gland is mediated by alpha adrenergic receptors; 2) the net amount of K+ released is the result of two opposing and almost simultaneous mechanisms, a passive extrusion and an active reuptake; 3) the active reuptake of K+ depends on the availability of energy and is mediated through the ouabain-sensitive Na+-K+ activated adenosine triphosphatase; 4) the reaction is critically dependent on the presence of Ca++ in the incubation medium and probably involves an influx of Ca++ upon stimulation with alpha adrenergic secretagogues.
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PMID:Potassium release from the rat submaxillary gland in vitro. I. Induction by catecholamines. 0 65


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