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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)

Adenosine diphosphatase (ADPase) activity was solubilized with a non-ionic detergent, Tween 20, from human umbilical vessels and purified to homogeneity by diethylaminoethyl-Sepharose CL-6B, adenosine 5'-monophosphate-Sepharose 4B, and concanavalin A-Sepharose chromatography. The apparent molecular mass was 75 kDa. The purified enzyme hydrolyzed pyrophosphate bonds of nucleoside di- and triphosphates in the presence of calcium ion. It was insensitive to the adenosine triphosphatase (ATPase) inhibitors, oligomycin and ouabain, and sensitive to sodium azide. Therefore, we concluded that the ADPase activity in human umbilical vessels does not derive from ADPase degrading only ADP but from ATP diphosphohydrolase (EC 3.6.1.5). The broad substrate specificity and the sensitivity to various inhibitors and calcium ion are common to ATP diphosphohydrolase from bovine aorta. However, there might exist some structural difference around the active site, because the antiserum raised in rabbit against the bovine aorta enzyme scarcely inhibited the human umbilical enzyme.
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PMID:Purification and characterization of adenosine diphosphatase from human umbilical vessels. 142 69

The kinetic properties of type-II ATP diphosphohydrolase are described in this work. The enzyme preparation from the inner layer of the bovine aorta, mostly composed of smooth muscle cells, shows an optimum at pH 7.5. It catalyzes the hydrolysis of tri- and diphosphonucleosides and it requires either Ca2+ or Mg2+ for activity. It is insensitive to ouabain (3 mM), an inhibitor of Na+/K(+)-ATPase, to tetramisole (5 mM), an inhibitor of alkaline phosphatase, and to Ap5A (100 microM), an inhibitor of adenylate kinase. In contrast, sodium azide (10 mM), a known inhibitor for ATPDases and mitochondrial ATPase, is an effective inhibitor. Mercuric chloride (10 microM) and 5'-p-fluorosulfonylbenzoyl adenosine are also powerful inhibitors, both with ATP and ADP as substrates. The inhibition patterns are similar for ATP and DP, thereby, supporting the concept of a common catalytic site for these substrates. Apparent Km and Vmax, obtained with ATP as the substrate, were evaluated at 23 +/- 3 microM and 1.09 mumol Pi/min per mg protein, respectively. The kinetic properties of this enzyme and its localization as an ectoenzyme on bovine aorta smooth muscle cells suggest that it may play a major role in regulating the relative concentrations of extracellular nucleotides in blood vessels.
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PMID:Kinetic properties of type-II ATP diphosphohydrolase from the tunica media of the bovine aorta. 147 95

An ATP diphosphohydrolase (EC 3.6.1.5) is an enzyme hydrolyzing pyrophosphate bonds in nucleoside di- and triphosphates with broad substrate specificity in the presence of divalent cations. The ATPase and ADPase activities in the enzyme purified to homogeneity from bovine aortic vessel wall were insensitive to oligomycin, ouabain, and various protease treatments, and sensitive to azide and Ap5A. Bovine aorta endothelial and smooth muscle cells were cultured separately to characterize the ectonucleotidase activities. The activities were dependent on the addition of divalent cations and had broad substrate specificity. The ecto-ATPase and -ADPase activities were insensitive to oligomycin, ouabain, and protease treatments, and sensitive to azide and Ap5A. No enzyme degrading only ADP was found in the aortic vessel wall. Moreover, antiserum raised against purified ATP diphosphohydrolase inhibited the ecto-ATPase and -ADPase activities. These results indicated that ecto-ATPase and ecto-ADPase are not separate enzymes but are expressed by one enzyme, ATP diphosphohydrolase.
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PMID:ATP diphosphohydrolase is responsible for ecto-ATPase and ecto-ADPase activities in bovine aorta endothelial and smooth muscle cells. 183 87

A true ecto-apyrase (ATP diphosphohydrolase, EC 3.6.1.5) enzyme was found in the synaptosomal fraction from the electric organ of the electric ray Torpedo marmorata. The activity could not be attributed to the combined action of different enzymes. The pH requirement and calcium dependence were the same for hydrolysis of both substrates ADP and ATP. The enzyme had an apparent Km value of 117 microM for ATP and of 123 microM for ADP. The involvement of nonspecific phosphatases in the hydrolysis of both substrates was excluded. The enzyme hydrolyses almost equally well different nucleoside di- and triphosphates. ATP and ADP hydrolysis was not inhibited by seven ATPase inhibitors, i.e., sodium azide, dinitrophenol, ruthenium red, oligomycin, ouabain, sodium orthovanadate and lanthanum.
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PMID:Characterization of a synaptosomal ATP diphosphohydrolase from the electric organ of Torpedo marmorata. 193 7

In the present study, we examined the ontogeny of ATP and ADP hydrolysis by cerebral cortex synaptosomes from rats of various ages (0-, 7-, 14-, 21- and 60 to 90-day-old rats) in order to learn whether hydrolytic activity increases during the period of intense brain growth, as has been reported for other enzymes involved in neurotransmitter metabolism. The results demonstrate that ATP and ADP hydrolyzing activities increase in parallel from birth until the second postnatal week (about 4-fold), followed by a slight and statistically insignificant increase until the animal reaches adulthood. The maximum increase in nucleotide hydrolysis coincided with maximum brain growth, which may indicate a role for the enzyme in neurotransmission. Furthermore, the parallel development of both activities (ATPase and ADPase) strongly suggest that a single enzyme, an ATP diphosphohydrolase, is involved in ATP and ADP hydrolysis by the synaptosomal fraction.
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PMID:Ontogeny of ATP and ADP hydrolysis by cerebral cortex synaptosomes from rats. 196 28

ATP diphosphohydrolase (EC 3.6.1.5) hydrolyzes pyrophosphate bonds of nucleoside di- and triphosphates in the presence of divalent cations. We purified the enzyme from the vessel wall of bovine aortas. The procedure gave a homogeneous preparation of ATP diphosphohydrolase for the first time from an animal source. Bovine aorta microsomes were treated with 50 mM bicarbonate buffer (pH 10.0) containing 0.025% Triton X-100. The enzyme was then solubilized from the microsomes with 0.5% Triton X-100 and purified to homogeneity by DEAE-Sepharose CL-6B chromatography and 5'AMP-Sepharose 4B affinity chromatography. The apparent molecular mass of the pure enzyme was 110 kDa. The activity recovered was 6% of that of the microsomes. The enzyme was more active with Ca2+ than Mg2+. The sensitivity of ADPase activity to divalent cations was higher than that of ATPase activity. The enzyme had broad substrate specificity to nucleoside di- and triphosphates.
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PMID:Purification of ATP diphosphohydrolase from bovine aorta microsomes. 254 Sep 63

Anti-aggregatory activities in bovine aorta microsomal fractions were solubilized with Triton X-100 and separated into two fractions by DEAE-Sepharose CL-6B. One fraction strongly inhibited arachidonic acid-induced platelet aggregation, and the other inhibited ADP-induced aggregation. The latter fraction contained ADPase activity. The ADPase activity was further purified by affinity chromatography. The purified enzyme had specific activities of 43.8 and 48.2 mumol of Pi/min/mg protein for ADP and ATP, respectively. The enzyme required calcium or magnesium ions and it was insensitive to ATPase inhibitors, namely oligomycin and ouabain, and to adenylate kinase inhibitor, Ap5A. Polyacrylamide gel electrophoretic experiments indicated that only one enzyme was involved. This was confirmed by the parallel behavior of ADPase and ATPase activities throughout all the purification steps. These results suggest that the main anti-aggregatory activity of bovine aorta microsomes for ADP-induced aggregation is due to an ATP diphosphohydrolase (EC 3.6.1.5).
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PMID:Purification and partial characterization of adenosine diphosphatase activity in bovine aorta microsomes. 282 77

The Mg2+-ATPase activities of bovine adrenal chromaffin granules were studied in highly purified preparations of granule ghosts and in intact organelles. The overall ATPase activity (150-250 nmol ADP min-1 mg-1) of the granule ghost preparations was inhibited less than 5% by the bathophenanthroline chelate of Fe(II), a potent inhibitor of mitochondrial F1-ATPase. This small inhibition can be accounted for by a very minor contamination with mitochondria or mitochondrial fragments. The overall ATPase activity of native granule ghosts was inhibited about 75% by N-ethylmaleimide, with half-maximal inhibition at about 20 microM. The titration curve was slightly shifted towards higher concentrations as compared to the inhibition curve for the proton pump activity, which was completely inhibited at 25 microM. N,N'-Dicyclohexylcarbodiimide inhibited the overall ATPase activity by 75-80% at 1.1 mumol/mg protein, a concentration that completely abolished the proton pump activity. Low concentrations (10 microM) of vanadate inhibited the overall ATPase activity by about 15% but had no effect on the proton pump activity, which was partly inhibited only at higher vanadate concentrations. Our attempts to assign a function to the vanadate-sensitive and N-ethylmaleimide-insensitive ATPase have so far been unsuccessful. In particular, our assay for ATP diphosphohydrolase activity was negative, although the chromaffin granule ghosts revealed a low Mg2+-ADPase activity (11.8 nmol AMP min-1 mg-1 protein). In intact chromaffin granules the specific Mg2+-ATPase activity (50-70 nmol ADP min-1 mg-1) was stimulated 2-fold by uncouplers, as compared to 1.6-1.7-fold in granule ghosts. The degree of energy coupling was rather independent of the external pH (6.5 less than pH less than 8.0) and temperature (20-45 degrees C). As expected, partial inhibition (about 15%) of the overall ATPase activity by 10 microM vanadate increased the ATPase control ratio. ADP was found to be a potent inhibitor of the proton pump activity with MgATP as the substrate, and the effect can partly be explained by a competitive type of inhibition of the hydrolytic reaction. This effect of ADP explains some of the kinetic data reported for MgATP-dependent (H+-ATPase-dependent) reactions in this organelle, notably the energy-dependent accumulation and storage of catecholamines.
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PMID:Studies on Mg2+-dependent ATPase in bovine adrenal chromaffin granules. With special reference to the effect of inhibitors and energy coupling. 288 84

Ouabain-sensitive (Na+ + K+)-ATPase activity in the rat myometrial microsome fraction could only be determined following detergent treatment. The (Na+ + K+)-ATPase activity manifested by detergent treatment proved very stable even to high concentrations of NaN3, in contrast Mg+-ATPase activity was reduced to about 30 percent of the control. The major part of the Mg2+-ATPase in the myometrial membrane preparation was found to be identical with the NaN3-sensitive ATP diphosphohydrolase capable of ATP and ADP hydrolysis. This monovalent-cation-insensitive ATP hydrolysis could be extensively reduced by DMSO. Furthermore DMSO prevented the inactivation of the (Na+ + K+)-ATPase activity. 10-100 microM Ca2+ inhibited the (Na+ + K+)-ATPase activity obtained in the presence of SDS by 15-50 percent. The Ca2+ sensitivity of the enzyme was considerably decreased if the proteins solubilized by the detergent had been separated from the membrane fragments by ultracentrifugation. The inhibitory effect could be regained by combining the supernatant with the pellet. Ca2+ sensitivity of the (Na+ + K+)-ATPase activity was preserved even after removal of the solubilized proteins provided that DMSO had been applied. It appears that a factor in the plasma membrane solubilized by SDS may be responsible for the loss of Ca2+ sensitivity of the (Na+ + K+)-ATPase activity, the solubilization of which can be prevented by DMSO.
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PMID:Myometrial (Na+ + K+)-activated ATPase and its Ca2+ sensitivity. 299 86

Solubilized Ca(++) + Mg(++)-dependent adenosinetriphosphatase (EC 3.6.1.3; ATP diphosphohydrolase) from sarcoplasmic reticulum increased bimolecular lipid membrane (oxidized cholesterol) conductance several hundred-fold. The relative conductance change and the relative permeability elicited by this material has the following sequence: Ba(++) > Ca(++) > Sr(++) > Mg(++) > Mn(++) > Zn(++), Na(+), K(+), Cs(+), Li(+), and Rb(+). Zn(++) and Na(+) strongly inhibit the increase in Ca(++) conductance obtained with solubilized Ca(++) + Mg(++)-dependent adenosinetriphosphatase. The Ca(++)-ionophore is an integral part of the Ca(++) + Mg(++)-dependent adenosinetriphosphatase enzyme and may function as a Ca(++)-carrier in the overall Ca(++)-pump of sarcoplasmic reticulum.
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PMID:A Ca++-dependent and -selective ionophore as part of the Ca++ plus Mg++-dependent adenosinetriphosphatase of sarcoplasmic reticulum. 427 8


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