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

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The role of the endothelium in response to aggregating platelets was examined in porcine coronary and peripheral (carotid, femoral and renal) arteries from normal and hypercholesterolemic pigs. Male Yorkshire pigs were fed either a normal diet or a 2% high cholesterol diet for 10 weeks. Endothelium-dependent responses were examined in vitro. In all arteries from control animals, aggregating platelets caused endothelium-dependent relaxations, which were augmented by ketanserin (a 5-HT2-serotonergic blocker), attenuated by apyrase (an adenosine diphosphatase and triphosphatase) or methiothepin (a combined 5-HT1 and 5-HT2-serotonergic blocker) and were almost abolished by a combination of apyrase and methiothepin. The platelet-induced relaxations were most pronounced in the coronary arteries. Adenosine diphosphate caused endothelium-dependent relaxations, which were significantly attenuated by apyrase. Serotonin also caused endothelium-dependent relaxations, which were significantly attenuated by methiothepin but augmented by ketanserin. The endothelium-dependent relaxations to adenosine diphosphate were most pronounced in coronary arteries and those to serotonin in coronary and renal arteries. In cholesterol-fed animals, the endothelium-dependent relaxations to aggregating platelets, adenosine diphosphate and serotonin were impaired in all four arteries. These experiments indicate that 1) the endothelium exerts inhibitory effects against aggregating platelets in porcine coronary and peripheral arteries; 2) platelet-induced endothelium-dependent relaxations are achieved by purinergic and 5-HT1-serotonergic receptors on the endothelium; and 3) hypercholesterolemia reduces the endothelium-dependent relaxations to aggregating platelets in a generalized manner because it impairs the relaxations to adenosine diphosphate and serotonin released from the platelets.
...
PMID:Hypercholesterolemia causes generalized impairment of endothelium-dependent relaxation to aggregating platelets in porcine arteries. 278 7

The present study examined the protective role of the venous endothelium against aggregating platelets and its modulation by diet. Yorkshire pigs were fed a regular chow (control pigs), 2% high-cholesterol diet (for 10 weeks, cholesterol-fed pigs), and regular chow plus cod-liver oil (30 ml/day for 4 weeks, oil-fed pigs). Endothelium-dependent responses were examined in vitro in rings of femoral veins in the presence of the inhibitor of cyclooxygenase indomethacin. In control pigs, aggregating platelets, serotonin, and ADP caused endothelium-dependent relaxations. The platelet-induced relaxations were attenuated by methiothepin (a combined 5-HT1 and 5-HT2 serotonergic blocker) or apyrase (an ADPase and ATPase) and were abolished by the combination of the two agents. In quiescent rings, platelets caused contractions, which were reduced in the presence of endothelium; the contractions were prevented by ketanserin (a 5-HT2 serotonergic blocker) or methiothepin but not by R 68 070 (a thromboxane A2 receptor blocker) or dazoxiben (a thromboxane-synthetase blocker). In cholesterol-fed pigs, the platelet-induced relaxations were not altered, whereas in oil-fed pigs, the endothelium-dependent relaxations to platelets, serotonin, and ADP were augmented. Platelet-induced contractions were significantly reduced in rings with endothelium from oil-fed pigs, whereas the contractions were comparable in rings without endothelium among the three groups. Endothelium-dependent relaxations in response to the calcium ionophore A23187, direct relaxations in response to sodium nitroprusside, and direct contractions in response to potassium chloride were comparable among the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Endothelium-dependent relaxation in response to aggregating platelets in porcine femoral veins and its modulation by diet. 278 11

The relative importance of intracellular and extracellular Ca2+ in the release of endothelium-derived relaxing factor (EDRF) and the mechanisms involved in the release of intracellular Ca2+ were investigated in cultured bovine endothelial cells. The release of EDRF by bradykinin, determined by bioassay, was dose-dependent showing an EC50 of 4 x 10(-10) M. The bradykinin-induced EDRF release from endothelial cells was maintained in the presence of extracellular Ca2+. However, in the absence of external Ca2+, bradykinin-induced EDRF release was both attenuated and transient. In cells loaded to isotopic equilibrium with 45Ca, bradykinin increased the 45Ca efflux into both calcium-containing and calcium-free solutions, with an EC50 for the increase in 45Ca efflux induced by bradykinin of 1.3 x 10(-9) M. The involvement of an intracellular Ca2+ store and the participation of a second messenger in its release were investigated in saponin-permeabilized endothelial cells. In saponin-permeabilized cells, ATP-sensitive calcium uptake was Ca2+,Mg2+ -ATPase-dependent. The ATP-sensitive uptake of calcium at different free Ca2+ concentrations showed at least two compartments involved in the uptake of Ca2+. The 45Ca uptake into the compartment with the lowest affinity and highest capacity could be inhibited by sodium azide, suggesting that this uptake was into mitochondria. The majority of the 45Ca uptake into the azide-insensitive store could be released by inositol-1,4,5-trisphosphate (IP3). The IP3-induced release was not affected by apyrase or exogenous GTP. The EC50 for the release of Ca2+ by IP3 was 1.0 microM and was unaffected by an inhibitor of IP3 breakdown (2,3-diphosphoglyceric acid).(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Bradykinin and inositol 1,4,5-trisphosphate-stimulated calcium release from intracellular stores in cultured bovine endothelial cells. 279 38

ATP methodology needs to be further standardized and improved in order to avoid the pitfalls that have sometimes hampered its application to biomass assays. The following steps have been reconsidered as far as the bacteriological applications is concerned: (a) destruction of free and somatic ATP: replacement of apyrase by mammalian ATPase, more readily accessible to specific inhibition; (b) extraction of bacterial ATP: protection of luciferase by lipids against inhibitory effect of cationic detergents with production of a constant light response. New methods are proposed for the calibration of luminometers and for the matching of sample holders in multichannel instruments. The limit of sensitivity of ATP assays is discussed in the light of currently available reagents and instruments.
...
PMID:Improved ATP methodology for biomass assays. 280 Dec 25

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).
...
PMID:Purification and partial characterization of adenosine diphosphatase activity in bovine aorta microsomes. 282 77

Mycelia of a low- and a high-production strain of Streptomyces aureofaciens were converted into protoplasts and divided into five subcellular fractions in order to localize exopolyphosphatases (EC 3.6.1.11), triphosphatase (EC 3.6.1.25), inorganic diphosphatase (EC 3.6.1.1), apyrase (EC 3.6.1.5) and glucokinase (EC 2.7.1.2). The highest specific activity of enzymes hydrolyzing polyphosphates was found in cytoplasmic vesicles and membranes. Triphosphatase was detected in the periplasmic fraction. Periplasmic vesicles and cytoplasm exhibited a high activity of diphosphatase. Apyrase was found mainly in the fractions of membranes and cytoplasmic vesicles. Glucokinase was a cytoplasmic enzyme. The enzymes were released from membrane structures into cytoplasm or periplasmic space if benzyl thiocyanate (10 microM) was present in the growth medium.
...
PMID:Subcellular localization of enzymes in Streptomyces aureofaciens and its alteration by benzyl thiocyanate. I. Phosphatases and ATP-glucokinase. 282 19

The (Na+ + K+)-activated ATPase catalyzes the K+-activated hydrolysis of 3-O-methylfluorescein phosphate (3OMFP) with a Km of 50 microM, nearly two orders of magnitude lower than the Km for nitrophenyl phosphate, 3 mM. Both ATP and nitrophenyl phosphate are competitors toward 3OMFP with Ki values corresponding to their Km values (for ATP that at the low-affinity sites of the E2 conformation). Enzyme treated with fluorescein isothiocyanate (FITC) such that 60% of the (Na+ + K+)-ATPase activity is lost still hydrolyzes both 3OMFP and nitrophenyl phosphate: the apparent Km values are increased less than 2-fold and the Vmax is unaffected. ATP still inhibits these K+-phosphatase reactions of the FITC-treated enzyme, and this inhibition can exceed the 40% of residual (Na+ + K+)-ATPase activity. Evaluation of a kinetic model indicates that the Ki for ATP is increased about an order of magnitude by FITC-binding. Similar results obtain with trinitrophenyl-ATP (TNP-ATP) as inhibitor, in this case with Ki values in the micromolar range. Finally, FITC treatment increases K+-activated ADPase activity. These observations are interpreted as the fluorescein ring of 3OMFP binding to the adenine pocket of the substrate site, thereby conferring high affinity, just as the fluorescein ring of FITC binding to the adenine pocket in the E1 conformation permits specific linkage of the isothiocyanate chain to a particular lysine, Lys-501. Then, coincident with the transition to the E2 conformation, which bears the low-affinity site for ATP and which catalyzes the K+-phosphatase reaction, the FITC molecule tethered to Lys-501 is pulled from the adenine pocket: allowing 3OMFP and ADP to bind as substrates and ATP and TNP-ATP as inhibitors, albeit in altered conformation. The E1 to E2 transition thus involves not only a change from high to low affinity for ATP, but also a distortion of the adenine pocket and the orientation between Lys-501 and Asp-369, the residue associated with catalysis.
...
PMID:Substrate sites of the (Na+ + K+)-ATPase: pertinence of the adenine and fluorescein binding sites. 282 69

Ca2+ uptake by microsomes prepared from guinea-pig stomach required the presence of both ATP and Mg2+ and was unaffected by NaN3. ATP-dependent Ca2+ uptake increased with increasing free Ca2+ concentration from 0.1 to 5 microM, and further increase in Ca2+ concentration above 5 microM did not enhance the uptake further. Half-saturation occurred at approximately 0.55 microM. The t1/2 values of Ca2+ loss from these vesicles loaded in the presence of oxalate were significantly slower than those in the absence of oxalate. Enzyme activity suggested linkage between Ca2+ uptake and ATPase activity, and most of the azide-sensitive component of ATP hydrolysis was attributable to potent inhibition of ADPase activity.
...
PMID:Characterization of Ca2+ transport and enzyme activity in microsomes isolated from guinea-pig stomach smooth muscle. 285 40

Transport of cytoplasmically synthesized precursor proteins into or across the inner mitochondrial membrane requires a mitochondrial membrane potential. We have studied whether additional energy sources are also necessary for protein translocation. Reticulocyte lysate (containing radiolabelled precursor proteins) and mitochondria were depleted of ATP by pre-incubation with apyrase. A membrane potential was then established by the addition of substrates of the electron transport chain. Oligomycin was included to prevent dissipation of delta psi by the action of the F0F1-ATPase. Under these conditions, import of subunit beta of F1-ATPase (F1 beta) was inhibited. Addition of ATP or GTP restored import. When the membrane potential was destroyed, however, the import of F1 beta was completely inhibited even in the presence of ATP. We therefore conclude that the import of F1 beta depends on both nucleoside triphosphates and a membrane potential.
...
PMID:Transport of F1-ATPase subunit beta into mitochondria depends on both a membrane potential and nucleoside triphosphates. 287 25

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.
...
PMID:Studies on Mg2+-dependent ATPase in bovine adrenal chromaffin granules. With special reference to the effect of inhibitors and energy coupling. 288 84


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---