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)

Net synthesis of adenosine 5'-triphosphate (ATP) in energy-depleted cells of Escherichia coli was observed when an inwardly directed protonmotive force was artificially imposed. In wild-type cells, ATP synthesis occurred whether the protonmotive force was dominated by the membrane potential (negative inside) or the pH gradient (alkaline inside). Formation of ATP did not occur unless the protonmotive force exceeded a value of 200 mV. Under these conditions, no ATP synthesis was found when cells were exposed to an inhibitor of the membrane-bound Ca2+- and Mg2+- stimulated adenosine triphosphatase (EC 3.6.1.3), dicyclohexylcarbodiimide, or to a proton conductor, carbonylcyanide-p-trifluoromethoxyphenyl-hydrazone. Adenosine triphosphatase-negative mutants failed to show ATP synthesis in response to either a membrane potential or a pH gradient. ATP synthesis driven by a protonmotive force was observed in a cytochrome-deficient mutant. These observations are consistent with the chemiosmotic hypothesis of Mitchell (1961, 1966, 1974).
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PMID:Protonmotive force as the source of energy for adenosine 5'-triphosphate synthesis in Escherichia coli. 0 27

Adenosine triphosphatase (ATPase) activated by Mg2+ or Ca2+ ions was detected in single mechanoreceptors (Pacini's corpuscles) of cat; addition of Ca2+ (10(-5)M) to Mg-ATP-ase increased the activity by the factor of 1.6. The activity optimum of Mg- or Co-ATPase was in the alkaline pH zone. A high substrate specificity of Mg, Ca-ATPase was shown. Parachlorinemercury-benzoate (5muM) considerably reduced the activity of Mg, Ca-ATPase, whereas oubain (10(-5)M) failed to affect it significantly. It is supposed that Mg, Ca-ATPase of Pacini's corpuscles was close to actomyosine -like proteins.
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PMID:[Mg, Ca-activated ATP-ase of Pacinian corpuscles]. 0 96

The Lubrol-dispersed guanylate cyclase from sea urchin sperm was purified and isolated essentially free of detergent by GTP affinity chromatography, DEAE-Sephadex chromatography, and gel filtration. After removal of the detergent, the enzyme remained in solution in the presence of 20% glycerol. The specific activity of the purified enzyme was about 12 mumol of guanosine 3':5'-monophosphate (cyclic GMP) formed - min-1 - mg of protein-1 at 30 degrees, an activity about 4600 times that of a soluble guanylate cyclase purified recently from Escherichia coli (Macchia V., Varrone, S., Weissbach, H., Miller, D.L., and Pastan, I. (1975) J. Biol. Chem. 250, 6214-6217). The cyclic GMP phosphodiesterase activity was negligible and adenosine 3':5'-monophosphate (cyclic AMP) phosphodiesterase was not detectable in the purified preparation. Cyclic AMP formation from ATP occurred at a rate of 0.002% of that of guanylate cyclase. In the absence of phosphodiesterase or guanosine triphosphatase inhibitors, 100% of the added GTP was converted to cyclic GMP. The purified enzyme required Mn2+ for maximum activity, the relative rates in the presence of Mg2+ or Ca2+ being less than 0.6% of the rates with Mn2+. The purified enzyme displayed classical Michaelis-Menten kinetics with respect to MnGTP (apparent Km is approximately equal to 170 muM) in contrast to the positively cooperative kinetic behavior displayed by the unpurified, detergent-dispersed, or particulate guanylate cyclase. The molecular weight of the purified enzyme was approximately 182,000 as estimated on Bio-Gel A-0.5m columns equilibrated in the presence or absence of 0.1 M NaCl. The unpurified, detergent-dispersed enzyme also migrated with an apparent molecular weight of 182,000 on columns equilibrated with 0.5% Lubrol WX and 0.1 M NaCl, but it migrated as a large aggregate (molecular weight is greater than 5 X 10(5)) on columns equilibrated in the absence of either the detergent of NaCl. After gel filtration, the unpurified, dispersed enzyme still yielded positive cooperative kinetic patterns as a function of MnGTP. Na dodecyl-SO4 gel electrophoresis of the enzyme after the DEAE-Sephadex or the gel filtration steps resulted in two major protein bands with estimated molecular weights of 118,000 and 75,000. Whether or not these protein bands represent the subunit molecular weights of guanylate cyclase is unknown at present.
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PMID:Sea urchin sperm guanylate cyclase. Purification and loss of cooperativity. 0 69

Adenosine triphosphatase (ATPase) activities were compared in platelets of asthmatic and nonasthmatic children. Significantly elevated Mg2+- and Ca2+-dependent ATPase activities were found in particulate and soluble fractions of platelets from nonsteroid-treated asthmatic children compared to steroid-treated asthmatic and nonasthmatic children. The most pronounced increase (greater than twofold) occurred in the Ca2+-ATPase of the soluble fraction which contains platelet contractile protein. Intact cell surface of ecto ATPase activity was not significantly increased in platelets of asthmatic children. The findings are consistent with adrenergic imbalance in asthma involving depressed adenylate cyclase activity (beta-adrenergic) and increased ATPase activity (alpha-adrenergic) and may relate to abnormal platelet aggregation patterns.
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PMID:Increased adenosine triphosphatase activity in platelets of asthmatic children. 12 27

A cell surface-located nucleoside triphosphatase activity can be assayed in liver epithelial cultures in situ with the incubation of intact cells in a medium containing [gamma-32P]adenosine triphosphate and correlated with the tumorigenicity of these cells in neonatal Wistar rats. The ectoenzyme activity of normal diploid cell lines is minimal, whereas a considerably high activity has been found in all tumorigenic cell lines tested. The optimum condition for the adenosinetriphosphatase activity is physiological with regard to osmolarity, ionic composition, pH, and substrate concentration in the medium. The enzyme is significantly stimulated by Ca2+, and its activation is controlled by Mg2+. Histochemical examinations indicate that glutaraldehyde-fixed cells of tumorigenic lines have Ca2+-stimulated adenosinetriphosphatase activity on the external surface. The isotopic assay of adenosine triphosphate hydrolysis by intact cells may provide a rapid method for screening oncogenesis in vitro of liver epithelial cells.
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PMID:Surface membrane nucleoside triphosphatase activity and tumorigenicity of cultured liver epithelial cells. 13 72

1. The specific activity of rat and pig liver nuclear-envelope nucleoside triphosphatase (EC 3.6.1.3) decreases when the system is depleted of RNA. The activity can be restored by adding high concentrations of yeast RNA to the assay medium. 2. Exogenous RNA also increases the activity of the enzyme in control envelopes (not RNA-depleted). The effect appears to be largely specific for poly(A) and poly(G); it is not stimulated by rRNA or tRNA preparations, ribonuclease-hydrolysed RNA, AMP, or double- or single-stranded DNA. 3. Inhibitors of the enzyme, in concentrations at which half-maximal inhibition of the enzyme is achieved, do not affect the percentage stimulation of the enzyme by yeast RNA. 4. The simulation is abolished by the inclusion of 150 mM-KCl or -NaCl in the assay medium, but not by increasing the assay pH to 8.5. 5. The results are discussed in the light of the possible role of the nucleoside triphosphatase in vivo in nucleo-cytoplasmic ribonucleoprotein translocation. 6. It is proposed that poly(G)-stimulated Mg2+-activated adenosine triphosphatase activity should be adopted as an enzymic marker for the nuclear envelope.
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PMID:Ribonucleic acid stimulation of mammalian liver nuclear-envelope nucleoside triphosphatase. A possible enzymic marker for the nuclear envelope. 14 Dec 76

A deoxyribonuclease was purified approx. 800-fold from crude extracts of the bacterium Alcaligenes faecalis. The enzyme requires ATP and Mn2+; ATP could be replaced by any other ribo- or deoxyribo-nucleoside triphosphate, and Mn2+ could be replaced by Mg2+ in 0.1 M-Tris/HCl, pH 8.0 at 37 degrees C. The enzyme could degrade linear duplex or denaturated DNA, but was inactive with closed-circular duplex DNA from bacteriophase PM-2. In the course of nucleolytic activity, ATP was hydrolysed. We have measured deoxyribonuclease and adenoxine triphosphatase activity in the presence of various salts, and found that the amount of ATP hydrolysis associated with a given amount of deoxyribonuclease activity was decreased in the presence of tetraethylammonium ions. Since these ions decrease the stability of the DNA helix, we conclude that one function of the ATP hydrolysis is to unwind the DNA.
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PMID:An adenosine triphosphate-dependent deoxyribonuclease from Alcaligenes faecalis. 14 25

A stable and homogeneous adenosine-5'-triphosphatase (ATPase, EC 3.6.1.3) has been solubilized from Rhodospirillum rubrum (R. rubrum) chromatophores by chloroform extraction. Purification of the Ca2+-dependent ATPase activity was 200-fold. Ca2+ can be replaced by Mg2+, Cd2+, and Mn2+. The Km for Ca-ATP (0.17 mM) is increased about 5-fold during solubilization of the enzyme, whereas the Km values for Mg-ATP (0.029 mM) and Cd-ATP (0.014 mM) are not affected. The chloroform-released ATPase has a molecular weight of 400,000 +/- 30,000 and consists of the following subunits (molecular weights in parenthesis): alpha(58,000), beta(53,500), gamma(39,000), delta(18,500), and epsilon(14,000). The amino acid composition and the fluorescence spectra are presented. Besides the chloroform-released ATPase complex three other Ca2+-dependent ATPase forms have been isolated from R. rubrum chromatophores by other methods for comparison. Ultrasonication of the membranes leads to the release of an ATPase complex which is mainly composed of alpha, beta, and gamma-subunits. From an acetone powder extract an ATPase complex could be purified by affinity chromatography which is composed of four kinds of subunits (alpha, beta, gamma, delta). The same acetone powder yields an ATPase consisting of only three different types of subunits (alpha, beta, gamma) if the final purification step is preparative disc electrophoresis on 6% polyacrylamide gels instead of affinity chromatography.
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PMID:Purification, subunit structure, and kinetics of the chloroform-released F1ATPase complex from Rhodospirillum rubrum and its comparison with F1ATPase forms isolated by other methods. 15 49

Activation of membrane-associated thiamin triphosphatase from rat brain requires a divalent cation (Mg2+, Ca2+, or Mn2+). The optimum concentration of Mg2+ necessary for maximal enzyme activity varies with substrate concentration; conversely, the maximal rate of hydrolysis attainbale by increasing thiamin triphosphate concentration is directly proportional to [Mg2+] for all levels of Mg2+ below that of the substrate. Under appropriate conditions, the Km of the thiamin triphosphatase for Mg2+ and for thiamin triphosphate are shown to be identical. Dissociation constants (Kd) for the binding of Mg2+ to thiamin triphosphate, thiamin diphosphate, and thiamin were determined; kinetic data re-expressed in terms of [Mg2+-thiamin triphosphate] conform to simple single substrate predictions, suggesting that the true enzyme substrate may be the Mg2+-thiamin triphosphate complex. Excess free Mg2+ inhibits thiamin triphosphatase activity competitively while excess free thiamin triphosphate in concentrations up to 10 times Km has no effect on the membrane-bound enzyme.
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PMID:Membrane-associated thiamin triphosphatase. II. Activation by divalent cations. 17 10

Membrane phosphorylation and nucleoside triphosphatase activity of sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle were studied using ATP and ITP as substrates. The Ca2+ concentration was varied over a range large enough to saturate either the high affinity Ca2+-binding site or both high and low affinity binding sites. In intact vesicles, which are able to accumulate Ca2+, the steady state level of enzyme phosphorylated by either ATP or ITP is already high in 0.02 mM Ca2+ and does not vary as the Ca2+ concentration is increased to 10 mM. Essentially the same pattern of membrane phosphorylation by ATP is observed when leaky vesicles, which are unable to accumulate Ca2+, are used. However, for leaky vesicles, when ITP is used as substrate, the phosphoenzyme level increases 3- to 4-fold when the Ca2+ concentration is raised from 0.02 to 20 mM. When Mg2+ is omitted from the assay medum, the degree of membrane phosphorylation by ATP varies with Ca2+ in the same way as when ITP is used in the presence of Mg2+. Membrane phosphorylation of leaky vesicles by either ATP or ITP is observed in the absence of added Mg2+. When these vesicles are incubated in media containing ITP and 0.1 mM Ca2+, addition of Mg2+ up to 10 mM simultaneously decreases the steady state level of phosphoenzyme and increases the rate of ITP hydrolysis. When ATP is used, the addition of 10 mM Mg2+ increases both the steady state level of phosphoenzyme and the rate of ATP hydrolysis. When the Ca2+ concentration is raised to 10 or 20 mM, the degree of membrane phosphorylation by either ATP or ITP is maximal even in the absence of added Mg2+ and does not vary with the addition of 10 mM Mg2+. In these conditions the ATPase and ITPase activities are activated by Mg2+, although not to the level observed in 0.1 mM Ca2+. An excess of Mg2+ inhibits both the rate of hydrolysis and membrane phosphorylation by either ATP or ITP.
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PMID:Calcium and magnesium regulation of phosphorylation by ATP and ITP in sarcoplasmic reticulum vesicles. 18 11


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