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 influence of an increased temperature (39 degrees C) on a denaturation of 50 kDa-fragment of myosin subfragment 1 was studied in the presence of different nucleoside triphosphates (NTP) and nucleoside diphosphates (NDP). The degree of the denaturation was appreciated evaluated from its trypsinolysis depth. According to their protective influence NTP and NDP were shown to arrange in lines ATP greater than or equal to CTP greater than UTP greater than GTP and ADP greater than GDP greater than CDP greater than UDP, correspondingly. The results received and the literature data allow to suggest that there are at least two states of ATPase site hydrophobic pocket, one of which in responsible for sharp ATPase reaction slowing-down on the stage of macroergic bonding splitting.
...
PMID:[Functionally different states of the "hydrophobic pocket" of the myosin ATPase center]. 183 76

The thermodynamic efficiency of the calmodulin-activated form of the Ca2+-pumping ATPase of the bovine cardiac sarcolemma (SL) was evaluated in sealed vesicles under reversible conditions. The free internal Ca2+ concentration ([Ca2+]i) established in the SL vesicle lumen by action of the ATPase was determined as a function of the [ATP]/([ADP][Pi]) ratio for the following experimental conditions: 250 mM sucrose, 100 mM KCl, 0.1 mM Mg2+, 25 mM HEPES, 25 mM Tris, pH 7.40, at 37 degrees C, [Ca2+]o = 50 nM (1 mM Ca/EGTA buffer), 0.75 mM Mg-ATP, 0.1 mM Pi, variable [ADP]. Under these conditions, with the pump working near its Km of 64 nM, the [Ca2+]i achieved was less than or equal to 18 mM, decreasing with increasing [ADP] for [ADP] greater than or equal to 0.84 mM. A plot of the square of the [Ca2+]i/[Ca2+]o ratio against [ATP]/([ADP][Pi]) gave a straight line with a slope of 1.5 x 10(7) M. This was in agreement, within the experimental error, with the equilibrium constant for ATP hydrolysis under these conditions (1.09 x 10(7) M). These results demonstrate (1) tight coupling between Ca2+ transport and ATP hydrolysis with a stoichiometry of 2 Ca2+ moved per ATP split and (2) a low degree of passive leakage. Analysis at low [ADP] (less than 0.83 mM) showed the unexpected result that ADP increases the rate of the forward reaction of the pump. The maximal effect on the initial rate is a 96 +/- 5% increase, with an EC50 of approximately 0.4 mM (ADP). Similar but lesser stimulation was observed with CDP. The implications of the above results for the energetics of the pump and for its physiological function in the beating heart are discussed.
...
PMID:The calmodulin-activated form of the Ca2(+)-pumping ATPase of the cardiac sarcolemmal membrane produces Ca2+ gradients with a thermodynamic efficiency of 100%. 213 38

Hexachlorocyclohexanes (HCCH) are chlorinated analogs of inositol; the alpha, beta, gamma, and delta isomers of HCCH have the stereochemical configurations of (+/-)-, scyllo-, muco-, and myo-inositol, respectively. To assess their potential as specific tools for the study of agonist-stimulated phosphoinositide metabolism, we examined the effects of these four HCCH isomers on phosphatidylinositol (PI) synthase (CDP-1,2-diacyl-sn-glycerol:myo-inositol 3-phosphatidyltransferase), PI:inositol exchange enzyme, and several membrane-associated enzymes unrelated to inositol metabolism. In pancreas microsomes, in the presence of saturating myo-inositol, the alpha, beta, gamma, and delta isomers (4 mM) inhibited PI synthase activity by 9, 4, 22, and 69%, respectively. Half-maximal inhibition by delta-HCCH occurred at 0.25 mM. A similar pattern of HCCH inhibition was obtained using n-octylglucopyranoside-solubilized and partially purified PI synthase preparations. The inhibition by delta-HCCH was noncompetitive versus myo-inositol. The PI:inositol exchange enzyme in mouse pancreas microsomes was inhibited 90% by 1 mM delta-HCCH in the presence of 0.25% Triton X-100, but not in its absence; half-maximal inhibition occurred with 0.5 mM delta-HCCH. delta-HCCH (4 mM) also inhibited to varying extents the following enzymes: pancreas CDP-choline:1,2-diacyl-sn-glycerol cholinephosphotransferase (75%), brain and erythrocyte (Na+,K+)-ATPase (87 and 70%), brain and erythrocyte Mg2+-ATPase (38 and -5%), brain 1,2-diacyl-sn-glycerol kinase (22%), and liver glucose 6-phosphatase (16%). gamma-HCCH (4 mM) inhibited these enzymes to a lesser extent, or not at all. The order of inhibition by HCCH stereoisomers was the same as the order of their saturation level in phospholipid vesicles (delta greater than gamma greater than alpha greater than beta). This suggests that the inhibitory action is due to insertion of the compounds either into hydrophobic domains of the enzymes or into annular lipid. The results indicate that the HCCHs are not selective inhibitors of inositol metabolism.
...
PMID:Inhibition of phosphatidylinositol synthase and other membrane-associated enzymes by stereoisomers of hexachlorocyclohexane. 257 70

A study was made of the activity of nucleoside diphosphatase (NDPase, EC 3.6.1.16) and nucleoside triphosphatase (NTPase, EC 3.6.1.15) that catalyze enzymatic dephosphorylation of UDP, CDP, UTP, and CTP in mitochondria and postmitochondrial supernatant fraction of rat liver 30 min, 1, 3, 6 and 24 h following 60Co-gamma-irradiation with a dose of 774 mC/kg. The observed phase changes in the enzyme activity depended on the times of exposure, a cell fraction, and nucleotides under study. Both uridylic and cytidylic nucleotides exhibited a significant increase in the their enzymatic disintegration being more pronounced at a comparatively later times, that is, 6 h, and particularly, 24 h after irradiation.
...
PMID:[Catabolism of pyrimidine nucleotides in the liver of irradiated animals]. 283 67

Sarcoplasmic reticulum (SR) and plasma membranes from canine left ventricle were used to evaluate the presence of the enzyme CDPdiglyceride-inositol transferase in these membranes. (K+,-Ca2+)-ATPase activity, a marker for SR, was 79.2 +/- 5.0 (SE) and 11.2 +/- 2.0 mumol.mg-1.h-1 in SR and plasma membrane preparations, respectively, and (Na+,K+)-ATPase activity, a marker for plasma membranes, was 5.6 +/- 1.2 and 99.2 +/- 8.0 mumol.mg-1.h-1, respectively. Contamination of SR and plasma membrane preparations by mitochondria was estimated to be 2% and 8%, respectively, and by Golgi membranes, 0.9% and 1.8%, respectively. Transferase activity, measured at pH 6.8, was 1.32 +/- 0.04 (SE) and 0.28 +/- 0.04 nmol of [3H]phosphatidylinositol ([3H]PtdIns).mg-1.min-1 in three SR and plasma membrane preparations, respectively. The transferase activity detected in the plasma membrane preparation could be accounted for largely, but not entirely, by contaminating SR membranes. The pH optimum for the SR transferase activity was between 8.0 and 9.0; little or no activity was detectable at pH 6.3 and 5.5, the lowest pH tested. Ca2+ inhibited the enzyme, half-maximal inhibition occurring at about 10 microM Ca2+; removal of the Ca2+ by addition of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid restored activity. No loss of [3H]PtdIns could be detected when membranes were incubated in the presence or absence of Ca2+. The Ca2+ inhibition of the transferase was noncompetitive with respect to CDP-dipalmitin while that with respect to myo-inositol was slightly noncompetitive at low [Ca2+] and became uncompetitive at higher [Ca2+].(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Presence of a Ca2+-sensitive CDPdiglyceride-inositol transferase in canine cardiac sarcoplasmic reticulum. 284 Sep 49

ATP analogues are studied for their effect on phosphatase and ATPase activities of Na+, K+-ATPase with the aim to obtain data concerning properties and structure of sites of high and low affinity to ATP. The activating effect of nucleotides on K+-dependent phosphatase reflecting their ability to be bound with the centres of high affinity decreases in a series: ATP, N1-oxy-ATP, CTP, JTP. In the domain of high ATP concentrations, where low affinity site is saturated, ADP is a competitive inhibition of ATPase reaction with Ki of 300 microM. The analysis of N1-oxy-ATP inhibiting effect has shown that its affinity to this site is six times less than that of ADP. The absence of the inhibiting effect of CDP, JDP, GDP and UDP in concentrations up to 10 mM testifies to the fact that sites of both low and high affinity to ATP are characterized by high specificity with respect to the adenine part of the substrate molecule.
...
PMID:[The effect of ATP analogues on ATPase and phosphatase activities of Na+, K+-ATPase for duck salt glands]. 298 68

The changes in fluorescence of 1-anilino-8-naphthalenesulfonate (ANS-) have been used to determine binding of ligands to the (Ca2+, Mg2+)-ATPase of sarcoplasmic reticulum vesicles, isolated from rabbit skeletal muscle. ANS- binds to sarcoplasmic reticulum membranes with an apparent Kd of 3.8 X 10(-5) M. The binding of ANS- had no effect on Ca2+ transport or Ca2+-dependent ATPase activity. EGTA, by binding endogenous Ca2+, increased the fluorescence intensity of bound ANS- by 10-12%. Subsequent addition of ATP, ADP, or Ca2+, in the presence or absence of Mg2+, reversed this change of fluorescence. The binding parameters, as determined by these decreases in fluorescence intensity, were as follows: for ATP, Kd = 1.0 X 10(-5) M, nH = 0.80; for ADP, Kd = 1.2 X 10(-5) M, nH = 0.89; and for Ca2+, Kd = 3.4 X 10(-7) M, nH = 1.8. The binding parameters for ITP and for the nonhydrolyzable analogue, adenyl-5'-yl-beta, gamma-methylene)diphosphate, were similar to those of ATP, but GDP, IDP, CDP, AMP, and cAMP had lower apparent affinities. Millimolar concentrations of pyrophosphate also decreased the fluorescence of bound ANS-, whereas orthophosphate caused a small (2-3%) increase in fluorescence in Ca2+-free media. Vanadate, in the presence of EGTA, decreased the fluorescence of bound ANS-with half-maximal effect at 4 X 10(-5) M. The changes of fluorescence intensity of bound ANS- appear to reflect conformational changes of the (Ca2+, Mg2+)-ATPase, consequent to ligand binding, with the low and high fluorescence intensity species corresponding to the E1 and E2 conformations, respectively. These appear to reflect similar conformational states of the (Ca2+, Mg2+)-ATPase to those reported by changes in intrinsic tryptophan fluorescence (DuPont, Y. (1976) Biochem, Biophys. Res. Commun. 71, 544-550).
...
PMID:Interaction of nucleotides and cations with the (Ca2+, Mg2+)-ATPase of sarcoplasmic reticulum as determined by fluorescence changes of bound 1-anilino-8-naphthalenesulfonate. 613 8

The active site of the myosin subfragment-1 ATPase was affinity-labeled with ribose-modified fluorescent analogs of ADP, dADP, CDP, UDP, IDP, and GDP in combination with vanadate, forming a stable myosin-nucleoside diphosphate-vanadate complex that is analogous to the normal myosin-ADP-Pi intermediate [Hiratsuka, T. (1984) J. Biochem. 96, 147-154]. Labeled enzyme was isolated free of unbound analog and vanadate, and fluorescent properties of the fluorophore at the active site were examined. Fluorescence emission and acrylamide quenching studies revealed that the hydrophobicity of environment around the fluorophore and the degree of its burial in the protein vary with the base structure of NDP. It was found that the fluorophore of ADP analog is most buried into the protein, while that of the GDP analog is least buried. The results suggest that the deep burial of ATP into the myosin active site is essential for muscle contraction.
...
PMID:Distinct structures of ATP and GTP complexes in the myosin ATPase. 623 21

The microsomal fraction (13 000 -60 000 x g pellet) from pea stem shows a very high divalent cation-dependent, diethylstilbestrol- and orthovanadate-inhibited ATPase and ADPase activity. No detectable inorganic or organic pyrophosphatase and adenylate kinase and almost negligible activities of mitochondrial ATPase and of other phosphomonoesterases are present in this preparation. The ATPase and ADPase activities of microsomes have been solubilized with NaClO4 and then purified by gel filtration and DEAE-Sephadex fractionation to a final specific activity of 71.5 and 102 mumol Pi/min per mg for ATP and ADP, respectively. The purified enzyme hydrolyzes triphosphonucleosides (ATP, CTP, GTP, UTP) and diphosphonucleosides (ADP and to a lesser extent CDP, UDP, IDP) and presents pH optima of 6 for ATP and 7 for ADP. It requires Mg2+, Mn2+ or Ca2+ and is inhibited by diethylstilbestrol and orthovanadate. The conclusion that the ATPase and ADPase activities belong to the same enzyme is based on the following results: (1) parallel effects of diethylstilbestrol and orthovanadate on both ATPase and ADPase; (2) parallel behavior of ATPase and ADPase throughout all the purification steps; (3) non-additivity of ATPase and ADPase and (4) lack of dilution of beta-32P formed from [beta-32P]-ATP by unlabelled ADP.
...
PMID:Purification and characterization of a divalent cation-activated ATP-ADPase from pea stem microsomes. 626 9

1. Parotid plasma membrane nonpump low-affinity Ca(2+)-ATPase, which possesses high-affinity (Ca2+ + Mg2+)-ATPase activity, was characterized. 2. Purified Ca(2+)-ATPase hydrolyzed the nucleoside triphosphates, GTP, ITP, CTP, UTP, TTP (67-93% of ATP) and nucleoside diphosphates, ADP, GDP, IDP, CDP, TDP (12-40% of ATP) but not AMP and p-NPP. 3. The maximum activities of Ca(2+)- and (Ca2+ + Mg2+)-ATPases were obtained in the presence of 1 mM and 0.13 microM Ca2+, respectively. 4. The Km values for Ca2+ in Ca(2+)- and (Ca2+ + Mg2+)-ATPases were 0.2 mM and 22 nM, respectively. 5. The activities of both Ca(2+)- and (Ca2+ + Mg2+)-ATPases were found in the right-side-out-vesicles obtained from the plasma membrane-rich fraction. 6. These features suggest that Ca(2+)-ATPase is an ecto-Ca(2+)-dependent nucleoside triphosphatase.
...
PMID:The possibility that Ca(2+)-ATPase from the plasma membrane-rich fraction of bovine parotid gland is ecto-Ca(2+)-dependent nucleoside triphosphatase. 806 15


1 2 Next >>

---