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PubMed1988

Inactivation of pyrophosphate-dependent phosphofructokinase from Propionibacterium freudenreichii by pyridoxal 5'-phosphate. Determination of the pH dependence of enzyme-reactant dissociation constants from protection against inactivation.

The pyrophosphate-dependent phosphofructokinase from Propionibacterium freudenreichii is rapidly inactivated by low concentrations of pyridoxal 5'-phosphate (PLP). The inactivation is first order with respect to PLP and the rate increases linearly with PLP concentrations suggesting that over the concentration range used no significant E-PLP complex accumulates during inactivation. The rate of inactivation decreases at high and low pH and this is discussed in terms of the mechanism of Schiff base formation. The presence of any reactants decreases the rate of inactivation to 0 at infinite concentration. This protection against inactivation has been used to obtain the pH dependence of the dissociation constants of all enzyme-reactant binary complexes. Reduction of the PLP-inactivated enzyme with NaB[3H]4 indicates that about 7 lysines are modified in free enzyme and fructose 6-phosphate protects 2 of these from modification. The pH dependence of the enzyme-reactant dissociation constants suggests that the phosphates of fructose 6-phosphate, fructose 1,6-bisphosphate, inorganic phosphate, and Mg-pyrophosphate must be completely ionized and that lysines are present in the vicinity of the 1- and 6-phosphates of the sugar phosphate and bisphosphate probably directly coordinated to these phosphates.

Algorithms↗
PubMedDate not supplied

[The influence of diphosphonic analogues of inorganic pyrophosphate on reactions catalyzed by DNA-dependent RNA-polymerase II].

Diphosphonic analogues of inorganic pyrophosphate were studied for their influence both on RNA pyrophosphorolysis and pyrophosphate exchange, catalyzed by purified DNA-dependent RNA-polymerase II from calf thymus. Methylene-, oxyethylene-and aminomethylenediphosphonic acids are shown to compete with PPi for incorporation into nucleoside triphosphate. They activate RNA pyrophosphorolysis in the concentration of 2 mM, but to a less extent than PPi does.

Animals↗
PubMed1979

Complexing of reduced technetium and tin(II) by chelating phosphate compounds. II. In vitro stability of pyrophosphate and ethane-1, hydroxy-1, diphosphonate (EHDP) complexes.

The in vitro stability of 99mTc- and 113Sn-pyrophosphate and ethane-1, hydroxy-1, diphosphonate (EHDP) complexes was studied by varying the mode of preparation. The 1-hr distribution in the rat was used as an indicator for complex formation or destruction. A maximum of bone uptake and urinary excretion and a minimum of soft tissue concentration was obtained if there was an excess of phosphate in relation to tin(II) in the equilibrium. Formation of tin(II) colloid was favoured in the presence of an excess of tin(II) in the equilibrium, 99mTc colloid occurred with some delay. After dilution in neutral normal saline the chelates were more or less destroyed, as shown by a 113Sn(II) colloid formation whereas the 99mTc-phosphate complexes were transformed into a 99mTc kidney agent. At pH 11 the 113Sn(II)-phosphate complexes proved to be stable, the 99mTc-phosphate complexes were also transformed into the 99mTc kidney agent. Oxidation of all tin(II) in the equilibrium by hydrogen peroxide did not change the distribution patterns of 113Sn, 99mTc was oxidized to pertechnetate. In general complexes between tin(II) and chelating phosphate compounds proved to be more stable than those with reduced technetium. EHDP was found to form stronger complexes with tin(II) and reduced technetium than pyrophosphate.

Animals↗
PubMed1985

Isoprenoid synthesis in isolated embryonic Drosophila cells. Sterol-independent regulatory signal molecule is distal to isopentenyl 1-pyrophosphates.

Embryonic Drosophila cells (Kc cells) were used to further characterize sterol-independent modulation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity. 3-Methyl-3-5-dihydroxyvalerate (mevalonate), 3-fluoromethyl-3,5-dihydroxyvalerate (fluoromevalonate), and 3-ethyl-3,5-dihydroxyvalerate (homomevalonate) were tested as modulators. Although mevalonate caused a rapid, reversible suppression of reductase activity, fluoro- and homomevalonate increased activity; fluoromevalonate was more effective than homomevalonate. Mevalonate, added simultaneously with fluoromevalonate, blocked the analogue's effect on Kc cell reductase activity. However, mevalonate did not suppress an established fluoromevalonate increase in HMG-CoA reductase activity. Fluoromevalonate blocked [1-14C, 5-3H]mevalonate conversion to 14CO2- and 3H-labeled lipids and [3H] mevalonate 5-pyrophosphate accumulated. Neither protein nor RNA synthesis were required for mevalonate-mediated suppression of reductase activity. However, fluoromevalonate's effect on reductase activity required protein synthesis. Furthermore, in the absence of protein synthesis, fluoromevalonate-stabilized Kc cell HMG-CoA reductase activity. We have concluded that mevalonate, fluoromevalonate, homomevalonate, and compactin (mevinolin) modulated HMG-CoA reductase activity because they altered isoprenoid carbon flow to a post-isopentenyl 1-pyrophosphate regulatory, signal molecule.

Animals↗
PubMed1979

Complexes of technetium with pyrophosphate, etidronate, and medronate.

The reduction of [99Tc]pertechnetate was studied as a function of pH in complexing media of pyrophosphate, methylene diphosphonate (MDP), and ethane-1, hydroxy-1, and 1-diphosphonate (HEDP). Tast (sampled d-c) and normal-pulse polarography were used to study the reduction of pertechnetate, and normal-pulse polarography (sweeping in the anodic direction) to study the reoxidation of the products. Below pH 6 TcO4-was reduced to Tc(III), which could be reoxidized to Tc(IV). Above pH 10, TcO4-was reduced in two steps to Tc(V) and Tc(IV), each of which could be reoxidized to TcO4-. Between pH 6 and 10 the results differed according to the ligand present. In pyrophosphate and MDP, TcO4- was reduced in two steps to Tc(IV) and Tc(III); Tc(III) could be reoxidized in two steps to Tc(IV) and TcO4-. In HEDP, on the other hand, TcO4- was reduced in two steps to Tc(V) and Tc(III), and could be reoxidized to Tc(IV) and TcO4-. Additional waves were observed; they apparently led to unstable products.

Diphosphates↗
PubMed1982

[Comparative effects of fluoride on three enzymes, hydrolyzing pyrophosphate - acid and alkaline phosphatases and inorganic pyrophosphatase].

The effects of fluoride on the activities of acid phosphatase (EC 3.1.3.2) from potato and alkaline phosphatase (EC 3.1.3.1) from E. coli during pyrophosphate and p-nitrophenylphosphate hydrolysis and on the activities of inorganic pyrophosphatase (EC 3.6.1.1) from baker's yeast during pyrophosphate hydrolysis were compared. For both phosphatases the type of interaction was found to be independent on the nature of substrate. For acid phosphatase and inorganic pyrophosphatase the inhibition was of non-competitive and uncompetitive types, respectively. In the case of alkaline phosphatase fluoride increased the rate of p-nitrophenol release during p-nitrophenylphosphate hydrolysis at pH greater than or equal to 7.9 without affecting the rate of phosphate release, which is indicative of fluorophosphate formation in the course of the transphosphorylation reaction. The data obtained suggest the existence of essential differences in the mechanisms of fluoride effects on the three enzymes under study.

Acid Phosphatase↗
PubMed1980

Enzymatic activities in cultured human lymphocytes that dephosphorylate dolichyl pyrophosphate and dolichyl phosphate.

Enzymatic activities which dephosphorylate dolichyl phosphate (Dol-P) and dolichyl pyrophosphate (Dol-P-P) have been observed in membranes from cultured human lymphocytes. Neither activity requires divalent metals. Dol-P phosphatase is inhibited by inorganic phosphate but not by other phosphate-containing compounds. Dol-P-P phosphatase is inhibited by bacitracin but not by phosphate-containing compounds including the methylene analogue of pyrophosphate. These reactions are similar to those previously found in the cycle of bacterial wall peptidoglycan biosynthesis. A chemical synthesis of [32P]Dol-P and [32P]Dol-P-P is reported.

Bacitracin↗
PubMed1980

Bone kinetics of calcium-45 and pyrophosphate labeled with technetium-96: an autoradiographic evaluation.

The uptake of calcium-45 and of pyrophosphate labeled with the long-lived technetium-96 isotope were compared by means of liquid-emulsion microautoradiograms of the epiphyseal plates of 10-week-old rabbits, at 30 min, and 3 and 48 hr after i.v. administration. For both tracers, thin sections confirm the significant role of the blood supply, especially shortly after injection. However, other more specific mechanisms lead to a mixing of the calcium in the mineral mass and to a linear deposition of technetium facing the osteoid surfaces. These findings suggest that the tropism of tin-reduced technetium pyrophosphate is not governed by the mineral pool but rather by exchanges inside a still poorly calcified organic matrix.

Animals↗
PubMed1980

[Pyrophosphate-99mTc scintigraphy in stenocardia patients].

The authors examined 166 patients with ischemic heart disease and attacks of angina pectoris and 21 healthy individuals. Scintigraphy, electrocardiography and tests for the activity of creatine phosphokinase and its MB fraction were carried out at rest, during physical exercise and 1--3 days after it. It was found that pyrophosphate-99mTc may accumulate in the myocardium both during the attack of angina pectoris and after its cessation. Angina pectoris may occur both with diffuse and with focal pyrophosphate-99mTc accumulation in the myocardium. Positive results of scintigraphy were encountered considerably more often in patients examined during physical exercise than in those examined at rest. Scintigraphic signs of angina pectoris which occurs under the effect of physical exertion develop less frequently, but persisted for a longer time than its electrocardiographic signs.

Adult↗
PubMed1980

[Clinical value of polyposition quantitative 99mTc-pyrophosphate and 99mTc-sulfur colloid scintigraphy in assessing the degree of spreading of tumorous process in lymphogranulomatosis].

To assess the degree of tumor proliferation radionuclide studies were performed in 187 patients with lymphogranulomatosis. Scintigraphy was conducted with 99mTc-pyrophosphate and 99mTc-sulfur colloid on gammer chambers FO GAMMA LFOV and OH 110 subsequently followed by processing a scintigraphic image on special-purpose computers CDP 11/34 and OH DC 160. The signs of bone affection revealed by 99mTc-pyrophosphate were supported in 86% of cases roentgenotomographically and histologically. A correlation between scintigraphic findings and the results of morphological studies in 45 patients showed a coincidence of the results in 93% of the cases with scintigraphy of the liver and in 81% of cases with radionuclide examination of the spleen by 99mTc-sulfur colloid. A statistical analysis has indicated that scintigraphic findings are consistent with histological ones qualitatively, the probability value being p > 0.999 (X2 = 15.35).

Colloids↗
PubMedDate not supplied

[The use of 99mTc-pyrophosphate indices in the quantitative evaluation of rheumatoid arthritis activity].

The authors have presented their own method of defining "joint to bone" and "joint to joint" radioactivity indicators with the application of 99mTc-pyrophosphate. Investigations of the degree of 99mTc-pyrophosphate accumulation in the 4 chosen points have shown that the lowest coefficient of changeability points out at half of crus length. The authors have employed radioactivity measurement of this place as a constant reference point while defining all the indicators "joint to bone". On the basis of the investigations carried out in 45 patients with varied degrees of rheumatoid arthritis activity and in the control group of twenty individuals it was established that the applied method makes possible the quantitative evaluation of rheumatoid arthritis activity in a simple way and in a short time.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Comparison of four methods of analysis of 99mTc pyrophosphate uptake in rheumatoid arthritic joints.

Knees, hands, forearms and thighs in 22 patients with classical rheumatoid arthritis and 18 controls were imaged with 99mTc pyrophosphate. The uptake of 99Tc pyrophosphate in the joints of the hand and knee was quantitated using a gamma camera interfaced to a computer. Quantitative measurements of joint activity were assessed by analyzing resultant data in a number of ways. Counts per unit area normalized for body weight and dose of radiopharmaceutical was found to be the most satisfactory method of quantitating differences in disease activity. However, the sensitivity of the method was not great enough to clearly distinguish normal and rheumatoid joints.

Arthritis, Rheumatoid↗
PubMed1980

[Possible participation of pyrophosphate in ADP and ATP biosyntheses from exogenous adenine by a culture of Corynebacterium species VSTI-301].

The autolyzing culture of Corynebacterium species VSTI-301 producing the synthesis of ATP from exogenous adenine was found to contain enzyme systems, which phosphorylate AMP into ADP and ADP into ATP in the presence of pyrophosphate. The optimal conditions for manifestation of activities of both systems in a cell-free extract were determined. One of the enzymes, i. e. pyrophosphate : ADP phosphotransferase, was isolated and purified 76-fold.

Adenine↗
PubMedDate not supplied

[Kinetic characteristics of the ATP-pyrophosphate isotope exchange catalyzed by RNA ligase from T4 bacteriophage].

The dependence of initial rate v0 of ATP--PPi exchange reaction catalyzed by RNA-ligase of bacteriophage T4 on the concentration of ATP(s), pyrophosphate (z) and Mgcl2 has been determined. The dependence of v0 on s and z described by the equation v0 = k-1k2E0/(k-1 + K2) (1 + K1/s + k2/z) has been obtained for the reaction of E + S in equilibrium ES in equilibrium E1 + Z, where E--enzyme, E1--adenylylenzyme, S--ATP, Z--pyrophosphate, K1 and K2--constants of equilibrium, k-1, k2--velocity constants of transition of ES to E + S and E1 + Z, E0--complete concentration of enzyme. The low inhibition of the ATP--PPi exchange by the acceptor A(pA)2 and donors pAp, p(Ap)3, pCp has been shown. The dependence of v0 on the concentration of MgCl2 is consent with the incorporation of only dimagnesium salts of substrates in the isotope-exchange reaction.

Adenosine Triphosphate↗
PubMed1984

Pyrophosphate of high and low energy. Contributions of pH, Ca2+, Mg2+, and water to free energy of hydrolysis.

The equilibrium between inorganic pyrophosphate and inorganic orthophosphate was determined at pH values varying between 6.0 and 8.0, in the presence of different concentrations of MgCl2, mixtures of MgCl2 and CaCl2, and different organic solvents. The reactions were catalyzed by yeast inorganic pyrophosphatase. It was found that at 35 degrees C, depending on the conditions used, the observed equilibrium constant of pyrophosphate hydrolysis vary from a value higher than 4 X 10(3) M (delta Goobs more negative than -5.1 kcal/mol) to a value as low as 3 M (delta Goobs -0.7 kcal/mol). The experimental data were used to compute the equilibrium constants of the reactions involving different ionic species. The data presented are interpreted according to the concept that the Keq of hydrolysis of a high energy compound depends on the difference in solvation energy of reactants and products.

Calcium Chloride↗
PubMedDate not supplied

[Pyrophosphate-dependent D-fructose-6-phosphate-phosphotransferase in Rhodospirillaceae (author's transl)].

A pyrophosphate-dependent fructose-6-phosphate phosphotransferase from the photosynthetic bacterium Rhodospirillum rubrum was partially purified and characterized in respect to kinetic and regulatory properties. The enzyme had a molecular weight of about 95 000 dalton and required Mg2+-ions for catalysis and maintenance of activity. The phosphotransferase was specific for fructose-6-phosphate (F-6-P) and inorganic pyrophosphate (PP) as substrates of the fructose-1,6-bisphosphate-forming reaction (forward reaction). In the phosphate (Pi)-dependent back reaction, the preferred substrate was fructose-1,6-bisphosphate (FBP). At optimal pH (7.2 for the forward, and 8.6 for the back reaction) the back reaction had a slightly higher Vmax than the forward reaction. The substrate-saturation curves of the enzyme were all hyperbolic with intersecting kinetic pattern. The Km-values (in mM) at saturating MgCl2-concentration were: 0.38 (F-6-P); 0.25 (PP); 0.02 (FBP) and 0.82 (Pi). The forward reaction was inhibited by ADP. The inhibition by ADP (Ki = 0.18 mM) was of the mixed type in respect to F-6-P, but independent of the PP-concentration. The inhibition by AMP (Ki = 0.017 mM) was of a more complex type, because AMP not only decreased the Vmax of the F-6-P- or PP-saturation curve, but also increased the Hill-coefficient from nH = 1 to nH = 2.5 of the F-6-P-saturation curve. The inhibition of the back reaction by the two adenylates was less pronounced. ATP (at 2.5 mM), like citrate, inhibited the back reaction only at low MgCl2 concentration (1 mM) indicating that the inhibitory effect was due to the chelation of Mg2+. Out of 5 other species of the Rhodospirillaceae tested, the PP-dependent phosphofructokinase was only shown to present in Rhodopseudomonas gelatinosa.

Kinetics↗
PubMed1984

Effect of zinc ions on farnesyl pyrophosphate synthetase activity.

Farnesyl pyrophosphate synthetases from pig and avian livers exhibit higher catalytic activities in the presence of 0.2 mM ZnCl2 than in the presence of MgCl2 or MnCl2 which are known to be required for enzyme activity. This is not the case for isopentenyl pyrophosphate isomerase or squalene synthetase.

Animals↗
PubMed1982

[Properties of 5-phosphoryl-1-pyrophosphate amidotransferase from the yeast Saccharomyces cerevisiae wild type and mutant with altered purine biosynthesis regulation].

The properties of partially purified 5-phosphoribosyl-1-pyrophosphate amidotransferase (EC 2.4.2.14) from S. cerevisiae 15V-P4 wild type and mutant aza 165 were studied. The latter is characterized by a higher sensitively of de novo purine synthesis to the inhibitory effect of exogenous guanine. Both enzymes were stable to short-term heating at 60 degrees. The rate of the enzyme-catalyzed reaction was dependent on the enzyme and substrate concentrations. Both enzymes had identical affinities for the substrates (Km for phosphoribosyl pyrophosphate was 0.44 mM for the wild type and 0.5 mM for mutant amidotransferase; Km for glutamine was 2.6 mM for both strains). No differences in the enzyme sensitivity to AMP and IMP inhibition were observed. There were essential differences in the sensitivity to inhibition by GMP: the level of inhibition was more than 80% for mutant amidotransferase and only 35% for the wild type enzyme. The inhibition with respect to phosphoribosylpyrophosphate for the former enzyme was of a mixed type, that for the wild type enzyme was of the "non-competitive" type. This feature of amidotransferase regulation in S. cerevisiae is the cause of the decreased sensitivity of de novo purine nucleotide biosynthesis to inhibition by exogenous guanine.

Amidophosphoribosyltransferase↗