Triphosphate Ions Research Articles

Effects of magnesium, manganese and adenosine triphosphate ions on pyruvate carboxylase from baker's yeast.

1. Pyruvate carboxylase from baker's yeast acts with either MgATP(2-) or MnATP(2-) as substrate. The optimum pH for the enzyme reaction is 8.0 with MgATP(2-) and 7.0 with MnATP(2-). 2. When the reaction velocity is plotted against MgATP(2-) (or MnATP(2-)) concentration slightly sigmoid curves are obtained, either in the presence or in the absence of acetyl-CoA (an allosteric activator). In the presence of excess of free Mg(2+) (or Mn(2+)) the curves turn into hyperbolae, whereas in the presence of excess of free ATP(4-) the apparent sigmoidicity of the curves increases. 3. The sigmoidicity of the plots of v against MgATP(2-) (or MnATP(2-)) concentration can be explained by the inhibitory effect of free ATP(4-), the concentration of which, in the experimental conditions employed, is significant and varies according to the total concentration of the ATP-magnesium chloride (or ATP-manganese chloride) mixture. Free ATP(4-) behaves as a negative modifier of yeast pyruvate carboxylase. 4. The effect of high concentrations of Mg(2+) (or Mn(2+)) on the kinetics of yeast pyruvate carboxylase can be explained as a deinhibition with respect to ATP(4-), instead of a direct enzyme activation. 5. At pH6.5 manganese chloride is more effective than magnesium chloride as enzyme activator even in the presence of a great excess (16-fold) of the latter. This is consistent with a significant contribution of the MnATP(2-) complex to the activity of yeast pyruvate carboxylase, in medium conditions resembling those existing inside the yeast cell (pH6.25-6.75; 12mm-magnesium chloride and 0.75mm-manganese chloride). 6. The physiological significance of the enzyme inhibition by free ATP(4-) is doubtful since the Mg(2+) and Mn(2+) concentrations reported to exist inside the yeast cell are sufficient to decrease ATP(4-) concentrations to ineffective values.

Complex formation between iron(II) and inorganic anions. Part II. The effect of oxyanions on the reaction of iron(II) with hydrogen peroxide

The increase in the bimolecular rate constant k0 for the reaction of iron(II) with hydrogen peroxide found with added halide ions is also observed with added sulphate, selenate, trimetaphosphate, and triphosphate ions. k0 increases to a limiting value which is different for each anion. Following the interpretation of the results with halide ions, 1:1 complexes of anions with FeII ions are found. Heats ΔH and entropies ΔS of formation of FeSO4, FeSeO4, FeHSO4+, FeHSeO4+, FeP3O9–, and FeHP3O9 are compared with ΔH and ΔS for the halogenoaquoiron(II) complexes and the hydroxoaquoiron(ii) ion. ΔH and ΔS are related to changes in the solvent structure induced by transferring the anion from bulk solvent to the FeII ion. Comparison is also made with ΔH and ΔS for other cation–ligand systems. Energies E and entropies ΔS* of activation for the reactions of these oxyanion aquoiron(II) complexes with H2O2 are compared with E and ΔS* for the reactions of halogenoaquoiron(II) complexes with H2O2.

Allosteric Activation of Sheep Kidney Pyruvate Carboxylase by the Magnesium Ion (Mg2+) and the Magnesium Adenosine Triphosphate Ion (MgATP2-)

Abstract The role of Mg2+ in the pyruvate carboxylase reaction has been investigated with kinetic methods. The results suggest that Mg2+ has at least two roles in the reaction mechanism; (a) it forms a complex with ATP4- to form the true MgATP2- substrate, and (b) it forms a complex with the enzyme to activate the enxymic reaction. The MgATP2- complex deviates from Michaelis-Menten kinetics in such a way as to indicate a homotropic cooperative effect involving at least 2 molecules of ligand. Excess Mg2+ induced a 3-fold stimulation of enzymic activity at saturating levels of MgATP2-. Excess Mg2+ causes changes in (a) the apparent Km value; (b) the slope of the Hill plot, and (c) the apparent Vmac when MgATP2- is the variable substrate. The apparent Km value for MgATP2- is found to be 6.6 x 10-4 m in the absence of free Mg2+ and 3.2 x 10-4 m in the presence of 1 x 10-3 m MgCl2. The apparent Km value for free Mg2+ is 2.5 x 10-4 m in the presence of 5.6 x 10-4 m MgATP2-. It is concluded that Mg2+ exhibits a heterotropic cooperative effect with respect to MgATP2-. Two possible mechanisms for the binding of Mg2+ and MgATP2- are suggested. Mg2+ may bind either at a specific effector site or, alternatively, at one of the binding sites for MgATP2- which is capable of functioning as an effector site. ATP4- was found to be a partial competitive inhibitor of MgATP2-.

A Soluble Fraction Requirement in the Transfer Reaction of Protein Synthesis by Rice Embryo Ribosomes

The requirements for the transfer of (14)C-phenylalanine from yeast soluble ribonucleic acid to protein in vitro by rice (Oryza sativa L. var. Bluebonnet) ribosomes have been investigated. An absolute requirement for polyuridylic acid, 2-mercaptoethanol, guanosine triphosphate, magnesium, and potassium or ammonium ions and ribosomes has been demonstrated. Ribosomes washed in 0.5% sodium deoxycholate also required the presence of rice supernatant. The optimum concentration of magnesium ion for the reaction was approximately 7 mm, while 60 mm of either ammonium or potassium ion gave maximum transfer of phenylalanine in this heterologous system. The optimum concentration of guanosine triphosphate required varied with the presence or absence of the phosphoenolpyruvate-pyruvate kinase generating system. Without the system, the optimum concentration was 1.5 mm, but in its presence the optimum was approximately 0.1 mm.

Transphosphorylation of Adenosine Di- and Tri-phosphates in the Presence of Calcium Phosphate Precipitates

IT has been discovered by Lowenstein1,2 that in dilute aqueous solution in the presence of certain divalent cations there is a tendency for the terminal phosphate group of the adenosine triphosphate ion (ATP) to be transferred to inorganic phosphate or other suitable acceptor. For example: where ADP represents the adenosine diphosphate ion. Krane and Glimcher3 have recently shown that a similar non-enzymatic transphosphorylation occurs on the surface of calcium phosphate crystals with hydroxyapatite structure when they are in contact with aqueous solutions of ATP. In this reaction the acceptor is phosphate belonging to the crystal. The rate of reaction is faster and less dependent on pH than that of Lowenstein.

Sodium tri(poly)phosphate in the kaolinite-water system

Rheological and sedimentation data have been obtained for the kaolinite-water system and quantitatively correlated with the adsorption of triphosphate ions from solution. The adsorption isotherms show very strong interaction between clay and triphosphate of a nature quite similar to that found for simpler complex formation between triphosphate and alkaline earth metal ions. The rate of hydrolysis of triphosphate is increased in the presence of kaolinite but the exact mechanism remains undetermined.

FEEDBACK CONTROL OF PURIFIED DEOXYCYTIDYLATE DEAMINASE.

The activity of purified deoxycytidylate deaminase obtained from chick-embryo extracts is dependent upon the presence of deoxycytidine triphosphate and magnesium ions. The stability of the enzyme at 37 degrees C is markedly enhanced by deoxycytidine triphosphate, and less so by the other deoxyribonucleotides. The inhibition by p-chloromercuribenzoate, urea, and deoxythymidine triphosphate, is reversed by deoxycytidine triphosphate. This reversal suggests that the regulation of enzyme activity is effected through configurational changes in the enzyme structure.

Phosphates and polyphosphates of the rare earth elements—III Cerium(III) tripolyphosphates

The reaction between cerium(III) chloride and sodium triphosphate solutions has been discussed. Evidences have been obtained that cerium(III) and triphosphate ions form two insoluble compounds in which the ratios Ce 3+: P 3O 10 5− are respectively 5 : 3 and 1 : 1. With excess triphosphate ions a stable solution is obtained. The characteristic absorption spectrum of cerium(III) chloride solutions is changed upon addition of excess sodium triphosphate as a result of the formation of relatively stable complex species. A new maximum between 300–304 mμ is observed. By the method of continuous variations, the complex is formed in the ratio Ce 3+ : P 3O 10 5− = 1 : 2, in the pH range of 3·0–9·5.

The Complexes of Calcium Ion with Pyrophosphate and Triphosphate Ions1

The Complexes of Calcium Ion with Pyrophosphate and Triphosphate Ions¹

The Complexes of Magnesium Ion with Pyrophosphate and Triphosphate Ions

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Complexes of Magnesium Ion with Pyrophosphate and Triphosphate IonsSheldon M. Lambert and James I. WattersCite this: J. Am. Chem. Soc. 1957, 79, 21, 5606–5608Publication Date (Print):November 1, 1957Publication History Published online1 May 2002Published inissue 1 November 1957https://doi.org/10.1021/ja01578a006RIGHTS & PERMISSIONSArticle Views404Altmetric-Citations80LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (375 KB) Get e-Alerts Get e-Alerts

The Complexes of Triphosphate Ion with Alkali Metal Ions1

The Complexes of Triphosphate Ion with Alkali Metal Ions¹

Reconstruction of coupled phosphorylation in the succinic oxidase system.

CALCIUM ions are known to inhibit oxidative phosphorylation in isolated mitochondria. As reported previously1, in the case of substrates oxidized via diphosphopyridine nucleotide, this inhibition can be reversed by the addition of the pyridine nucleotide, adenosine triphosphate and manganous ions. Treatment with the pyridine nucleotide alone partially restores only the respiration; but addition of all three factors is necessary in order to re-establish both oxidation and phosphorylation.