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:3.6.1.25 (triphosphatase)
1,529 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The properties of a cell surface nucleoside 5'-triphosphatase have been studied in small, intact, frog skeletal muscles, as a means of distinguishing the enzyme from other adenosine 5'-triphosphatases and of understanding its behaviour in the muscle membrane. The ectoenzyme in situ was shown to be a Ca2+- or Mg2+-activated ATPase liberating 7.5 +/- 0.4 (mean +/- SEM, n = 30) mumol of inorganic phosphate/g of muscle per 20 min, when the muscle was exposed to 2 mM ATP and 2 mM Ca2+ in Ringer's solution. The apparent Km for Mg2+ was 0.74 mM and for Ca2+ was 0.23 mM. A residual ATPase activity (20%) was found in the complete absence of divalent cations suggesting the existence of two ATPase types. A broad specificity toward nucleoside 5'-triphosphates was exhibited by the ecto-ATPase, but there was no nonspecific phosphatase activity. The enzyme was inhibited by La3+ and Cd2+, but was insensitive to ouabain, 2,4-dinitrophenol, oligomycin, and ruthenium red. Thus the ectoenzyme was not a Na+, K+-transport ATPase, was not an ATPase of mitochondrial origin, or a Ca2+-transport enzyme. Insulin had no effect. Inhibition by mersalyl, carbodiimide, and polar and cross-linking nonpolar nitrobenzene derivatives suggested that, for maximum activity, this membrane-bound enzyme required free sulfhydryl groups, certain free carboxyls, and an appreciable degree of hydrophobicity in its microenvironment.
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PMID:Characteristics of skeletal muscle ecto-ATPase in situ. 615 Jul 52

Upon incubation with trypsin, the adenosine-5'-triphosphatase (ATPase) activity of the nucleotide-depleted F1 is first rapidly and slightly activated and then slowly inactivated. The first phase is simultaneous with the conversion of the alpha subunit into an alpha' fragment which migrates between alpha and beta on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The second phase is related to the proteolysis of the three main subunits, alpha', beta, and gamma. Preincubation of the enzyme with low concentrations of adenosine 5'-diphosphate (ADP) or adenosine 5'-triphosphate (ATP) does not modify the slight increase of activity but efficiently prevents the inactivation induced by trypsin. The alpha leads to alpha' conversion is not affected whereas the further proteolysis of alpha', beta, and gamma does not occur. On the contrary, even high concentrations of GDP only slightly lower the trypsin-induced inactivation. The presence of endogenous tightly bound nucleotides also partially lowers the sensitivity to trypsin since F1 is less rapidly inactivated and proteolyzed than the nucleotide-depleted F1. Phosphate, at high concentrations, both slows down the first phase of activation and simultaneous alpha leads to alpha' conversion and prevents the second phase of inactivation and proteolysis of the main subunits. Pretreatment of the nucleotide-depleted F1 with trypsin under conditions where the ATPase activity is largely inhibited only slightly modifies, however, the hysteretic behavior of the enzyme: the ADP binding and the concomitant hysteretic inhibition of the residual activity are not markedly diminished. The purified ATPase-ATP synthase complex binds very few ADP's and is not hysteretically inhibited. Its ATPase activity is rapidly activated but not further inhibited by trypsin. Preincubation of the complex with ADP does not modify the effects of trypsin.
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PMID:Use of trypsin to monitor conformational changes of mitochondrial adenosinetriphosphatase induced by nucleotides and phosphate. 622 Jul 37

Adenosine triphosphatase (ATPase) activity of flagella isolated from ejaculated bull sperm was solubilized by 5 min exposure to 0.6 M KCl at 4 degrees C. ATPase activity in the flagellar extract was characterized with respect to enzyme, substrate, activator ion, salt, and hydrogen ion concentration. Flagellar extract required the presence of a divalent cation for activity: Mg2+, Ca2+, or Mn2+ could function as activator, but Zn2+ or Cd2+ could not. Magnesium-activated ATPase was maximal in the presence of Mg2+ and ATP in equimolar concentrations and at alkaline pH. Calcium activated ATPase was maximal over a wide range of Ca2+:ATP ratios and at pH 8.0. The presence of increasing concentrations of Na+ and/or K+ ions in the assay medium (0.5-300 mM) had no effect on the ATPase activity of flagellar extract.
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PMID:Studies on the flagellar ATPase of bull spermatozoa: extraction and characterization. 622 99

Adenosine triphosphatase activity which is Mg2+-dependent and stimulated by submicromolar concentrations of Ca2+ (as Ca . ATP) was identified in the total particulate fraction of rat pancreatic acini. Half-maximal activity (V0.5) is obtained at 100.1 +/- 6 nM Ca . ATP with a Hill coefficient of 2.2 +/- 0.1 (mean +/- S.E.; n = 4). Maximal activity was 75 +/- 19 pmol of Pi released from ATP minute-1 microgram of membrane protein-1 (mean +/- S.E.; n = 7). High affinity Ca2+-ATPase activity was unaffected by ouabain, Na+, K+, La3+, and added calmodulin. Activity was slightly reduced by ruthenium red (0.1 mM) and by oligomycin (80 micrograms/ml) but was reduced almost 50% by the phenothiazine derivative fluphenazine in a dose-related and Ca2+-dependent manner. Hydrolysis of p-nitrophenyl phosphate was 9% of the rate of ATP hydrolysis and was independent of Ca2+ concentration. However, ADP, GTP, UTP, and ITP were hydrolyzed at 76-93% the rate that ATP was hydrolyzed with V0.5 values and Hill coefficients similar to those of Ca . ATP. We conclude that rat pancreatic acini contain an enzyme for active Ca2+ translocation: ATPase activity that is Mg2+-dependent and stimulated by submicromolar concentrations of Ca . ATP. Substrate hydrolysis appears to involve positive cooperative interactions of multiple ligand-binding sites and may be regulated in part by calmodulin.
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PMID:High affinity, calcium-stimulated adenosine triphosphatase activity in the particulate fraction of rat pancreatic acini. 623 78

Basal lateral membrane vesicles were isolated from rat intestinal epithelial cells. The sodium potassium triphosphatase (Na/K-ATPase) of these plasma membranes has been characterized by (1) the molecular weight of the phosphorylated intermediate, (2) the sensitivity of the phosphorylated intermediate to hydroxylamine, (3) its ouabain binding constants, and (4) its susceptibility to digestion by pronase. The phosphorylated intermediate was shown by SDS polyacrylamide gel electrophoresis to be a protein of 100,000 Daltons apparent mol wt. Its extensive hydrolysis in hydroxylamine demonstrated that it was an acyl phosphate. The isolated basal lateral membranes bound ouabain with a dissociation constant, Km (1.5 x 10(5) M), similar to the inhibitory constant KI (3 X 10(-5) M), measured for ouabain inhibition of the Na/K-ATPase activity. The association rate constant measured for ouabaiation rate constants reported for other tissues and species. The high dissociation rate constant 3.6 x 10(-2) sec-1, is consistent with the insensitivity of the rat to ouabain. Digestion of the intact cells by pronase yielded basal lateral membranes in which the Na/K-ATPase had been unaffected. The phosphorylated intermediate ran as a sharp band at 100,000 Daltons on electrophoresis, and the ouabain dissociation constant appeared to be unchanged. In these membranes, protein stains of polyacrylamide gels revealed digestion of the major high mol wt proteins including the major protein at 100,000 Daltons. This suggests that the Na/K-ATPase represents a minor component, less than 1%, of the basal lateral membrane protein. From these characteristics of the phosphorylated intermediate and the ouabain binding constants, we conclude that the Na/K-ATPase of the basal lateral membranes of rat intestinal epithelial cells is similar to that found in other tissues and species. Estimates of the number of pump sites and the turnover number predict rates of Na transport that are consistent with observed values.
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PMID:Some characteristics of Na/K-ATPase from rat intestinal basal lateral membranes. 624 95

A cytochemical technique that measures the ability of plasma to stimulate guinea-pig renal glucose-6-phosphate dehydrogenase (G6PD) activity in vitro, which is a marker of its ability to inhibit Na+-K+-adenosine-triphosphatase (Na+-K+-ATPase), was used in 19 patients with essential hypertension and 23 normotensive, healthy subjects. The ability of plasma to stimulate G6PD was significantly greater in the hypertensive patients when they were taking their normal sodium diet than in the normotensive subjects, and was significantly correlated with blood pressure. The ability of plasma to stimulate G6PD was inversely correlated with plasma renin activity in the hypertensive patients and increased with age and sodium intake in the normotensive subjects. These results support the hypothesis that essential hypertension, and also perhaps the increase in blood pressure with age in communities that consume large quantities of salt, is in part due to an increase in a circulating concentration of an inhibitor of Na+-N+-ATPase.
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PMID:Evidence for a raised concentration of a circulating sodium transport inhibitor in essential hypertension. 627 73

The effect of vanadate (0.5 mumol/min) on renin secretory rate (RSR) of the kidney has been studied in nembutal-anesthetized, volume-expanded dogs. Intrarenal vanadate infusion caused a 69.3 +/- 8.8% decrease in RSR. This was accompanied by marked decreases in renal blood flow (RBF), glomerular filtration rate (GFR) and fractional excretion of sodium (FENa). Renal vascular resistance rose from 1.3 +/- 0.09 to 6.1 +/- 2.3 mm Hg/ml/min (P less than .0005). Papaverine infusion partially blunted the effect of vanadate on RSR (RSR only fell to 42. +/- 10% of basal values). The decreases in RBF and GFR were also less and FENa slightly higher than normal. Acetylcholine prevented the effects of vanadate more fully. There was no fall in RBF, GFR or FENa and it basically abolished the fall in RSR which fell only 19.4 +/- 25.3 of control (P = N.S.). Nifedipine (a slow Ca++ channels blocker) also prevented the fall in RBF, GFR and FENa induced by vanadate. RSR did not change significantly (7.8 +/- 10.9%). These results clearly demonstrate that vanadate is a potent inhibitor of renin secretion and suggest that inhibition of smooth muscle Na+, K+, adenasine triphosphatase and changes in the cystosolic concentration of Na and Ca are involved in its mechanism. Changes in perfusion pressure and sodium delivery to the macula densa appear to have little if any role in the inhibition.
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PMID:Effect of sodium orthovanadate on renal renin secretion in vivo. 628 12

Adenosine triphosphatase activity of U. urealyticum is an integral membrane-bound protein which cannot be detached from the membrane by mild treatment with EDTA in low-ionic strength media nor by ionic detergents which rapidly inactivated the enzyme. The enzyme was Mg++ dependent; Mn++ and Co++ could replace Mg++ to some extent. A slight stimulatory effect was also exerted by sodium and lithium. The enzyme showed a nucleotide triphosphatase activity, but ADP was hydrolyzed at close to 40% the rate of ATP and other nucleotide monophosphatase were hydrolyzed at a very slow rate. Oubain and oligomycin did not inhibit the adenosine triphosphatase activity, whereas DCCD, NBD-Cl and several sulfhydryl-blocking reagents strongly reduced its activity. The enzyme could not be stimulated by trypsin pretreatment. It seems that the complex enzyme is tightly linked to the lipid bilayer of the membrane and differs in many aspects from the F0-F1 (Mg++, Ca++)-ATPase of bacteria.
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PMID:Adenosine triphosphatase activity of Ureaplasma urealyticum. 628 75

The direct addition of insulin to highly purified nuclear envelopes prepared from the livers of diabetic rats resulted in a decrease in the incorporation of 32P into trichloroacetic acid-precipitable proteins. Autoradiography of 32P-labeled envelopes, solubilized in sodium dodecyl sulfate and subjected to electrophoresis, revealed that insulin decreased the phosphorylation of all major protein bands. Insulin produced detectable effects at concentrations between 0.1 and 1 pM, maximal effects at 10 pM, and progressively diminished effects at higher concentrations. Two insulin analogs, desdipeptide proinsulin and desoctapeptide insulin, had approximately 10% and 1%, respectively, the activity of native insulin. When nuclear envelopes were first phosphorylated with [gamma-32P]ATP and insulin was then added with an excess of unlabeled ATP, dephosphorylation was enhanced, suggesting that insulin was regulating nuclear envelope phosphatase activity. The direct addition of insulin to isolated rat liver nuclei in the presence of ATP stimulated the release of previously 14C-labeled trichloroacetic acid-precipitable mRNA-like material, and the direct addition of insulin to nuclear envelopes stimulated the activity of nucleoside triphosphatase, the enzyme that participates in mRNA nucleocytoplasmic transport. Moreover, the dose-response curves for these functions mirrored insulin's inhibition of nuclear envelope phosphorylation. These data suggest, therefore, a mechanism whereby insulin directly inhibits the phosphorylation of the nuclear envelope, leading in turn to the regulation of mRNA metabolism.
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PMID:Insulin regulation of protein phosphorylation in isolated rat liver nuclear envelopes: potential relationship to mRNA metabolism. 629 83

The sodium-potassium activated and magnesium dependent adenosine-5'-triphosphatase (Na(+)-K+/Mg+2 ATPase EC 3.6.1.3.) activity and lipid peroxidation and early ultrastructural findings are determined in rat spinal cord at the early stage of trauma produced by a surgical clip on the thoracal 2-7 segments. The effect of treatment with intravenous methylprednisolone (MP) was evaluated the basis of these biochemical alterations and ultrastructural findings in the same model. The specific activity of the membrane bound enzyme Na(+)-K+/Mg+2 ATPase was promptly reduced in as early as ten minutes following spinal cord injury and remained at a level lower than the levels in the control group and in the sham-operated group. Methylprednisolone treatment immediately after the trauma attenuated the inactivation of Na(+)-K+/Mg+2 ATPase. On the other hand, there was significant difference in lipid peroxide content between the sham-operated and the injured animals. Methylprednisolone treatment reduced thiobarbituric acid reactive substance (TBARS) content in Group IV. We determined a positive relationship among membrane-bound enzyme Na+K+/Mg+2 ATPase activity, malondialdehyde (MDA) content and early ultrastructural changes in the traumatized and treated groups.
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PMID:Correlation of alterations on Na(+)-K+/Mg+2 ATPase activity, lipid peroxidation and ultrastructural findings following experimental spinal cord injury with and without intravenous methylprednisolone treatment. 756 28


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