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PubMed1999

Aluminum Polyphosphate Nanoparticles: Preparation, Particle Size Determination, and Microchemistry.

Admixture of aluminum nitrate, sodium polyphosphate, and ammonium hydroxide solutions yields stable dispersions of hydrated aluminum polyphosphate particles within a broad reagent concentration range. These particles are formed by liquid-liquid phase separation, for which a phase diagram was calculated using suitable models for concentrated electrolyte solutions. Particle effective diameters range from a few nanometers to many hundreds and are fractionated by centrifugation. Particle electrophoretic mobility is very low and the hydration degree is high ( approximately 80% v/v). Dry nanoparticles (1- to 15-nm diameter as observed by TEM) as well as particle aggregates are obtained by lyophilization. Element (P, Al, and Na) mapping by ESI-TEM shows that particle aggregates have a core-and-shell morphology, with a higher content of P in the aggregate core and a higher Na content at the outer shell. Copyright 1999 Academic Press.

Journal Article↗

PubMed1976

Polyphosphate granules in encysted zoospores of Rozella allomycis.

Methods of ultracytochemistry and of X-ray energy dispersive analysis have been used to demonstrate that the "gamma-like" granules in encysted zoospores of the chytrid Rozella allomycis contain polyphosphate. The possibility that cysts contain two classes of polyphosphate granules which differ in structure, in function, and in origin is discussed.

Cytoplasmic Granules↗

PubMed1975

Formation of nucleoside 5'-polyphosphates from nucleotides and trimetaphosphate.

When solutions of nucleoside 5'-phosphates and trimetaphosphate are dried out at room temperature, nucleoside 5'-polyphosphates are formed. The Mg++ ion shows a superior catalytic function in this reaction when compared with other divalent metal ions. Starting with nucleoside 5'-phosphates, Mg++ and trimetaphosphate, the predominant products in the nucleoside 5'-polyphosphate series pnN are p4N, P7N and p10N. Nucleoside 5'-diphosphates yield p5N and p8N, nucleoside 5'-triphosphates give p6N and p9N. The prebiological relevance of these reactions is discussed.

Adenine Nucleotides↗

PubMed1998

Effects of adenosine 5'-triphosphate, uridine 5'-triphosphate, adenosine 5'-tetraphosphate and diadenosine polyphosphates in guinea-pig taenia caeci and rat colon muscularis mucosae.

The functional effects of adenosine 5'-triphosphate (ATP), uridine 5'-triphosphate (UTP), adenosine 5'-tetraphosphate (AP4) and the diadenosine polyphosphates P1,P3-diadenosine triphosphate (Ap3A), P1,P4-diadenosine tetraphosphate (Ap4A) and P1,P5-diadenosine pentaphosphate (Ap5A) were studied in two isolated smooth muscle preparations thought to contain P2Y (P2Y1) receptors, the guinea-pig taenia caeci (which relaxes to ATP) and the rat colon muscularis mucosae (which contracts to ATP). In addition, the breakdown of these compounds by the rat colon muscularis mucosae was investigated by high pressure liquid chromatography. In the guinea-pig taenia caeci all the purine nucleotides caused relaxation with a potency order of Ap3A=Ap4A> ATP>AP4=Ap5A, and these relaxations were antagonised by suramin with apparent pA2 values in the region of 5, consistent with activation of a P2Y1 receptor. In the rat colon muscularis mucosae the nucleotides caused contraction with a potency order of Ap3A = Ap4A>ATP=AP4 =Ap5A >UTP. However, while suramin (100 microM) inhibited responses to ATP and UTP at all concentrations of agonist, it only inhibited contractions induced by the higher concentrations of AP4, Ap3A and Ap4A and had little effect on contractions induced by Ap5A. A higher concentration of suramin (1 mM) enhanced contractions induced by ATP but greatly inhibited those induced by UTP and had no effect on responses to the other agonists. The A1 adenosine receptor antagonist 1,3-dipropyl-8-cyclopentylxanthine (DPCPX; 10 nM) had no effect on responses to ATP or UTP but inhibited responses to Ap3A, Ap4A, Ap5A and AP4. A combination of suramin (1 mM) and DPCPX (10 nM) almost abolished responses to all the agonists. ATP and UTP were rapidly degraded by the rat colon muscularis mucosae while AP4, Ap3A, Ap4A and Ap5A were degraded more slowly, and the major product detected after breakdown of the purine nucleotides was inosine rather than adenosine. The breakdown of all the nucleotides was inhibited by suramin (1 mM), although this inhibition did not achieve statistical significance in the case of ATP. These results show that while the diadenosine polyphosphates appear to act as P2 agonists in the taenia caeci, in the rat colon muscularis mucosae their major action is via adenosine A1 receptors rather than via P2 receptors. In addition, although they are more stable than ATP or UTP, their action in this tissue is clearly affected by their degradation which complicates the effects of suramin.

Adenine Nucleotides↗

PubMed2006

Dinucleoside polyphosphates and their interaction with other nucleotide signaling pathways.

Dinucleoside polyphosphates or Ap(n)A are a family of dinucleotides formed by two adenosines joined by a variable number of phosphates. Ap(4)A, Ap(5)A, and Ap(6)A are stored together with other neurotransmitters into secretory vesicles and are co-released to the extracellular medium upon stimulation. These compounds can interact extracellularly with some ATP receptors, both metabotropic (P2Y) and ionotropic (P2X). However, specific receptors for these substances, other than ATP receptors, have been described in presynaptic terminals form rat midbrain. These specific dinucleotide receptors are of ionotropic nature and their activation induces calcium entry into the terminals and the subsequent neurotransmitter release. Calcium signals that cannot be attributable to the interaction of Ap(n)A with ATP receptors have also been described in cerebellar synaptosomes and granule cell neurons in culture, where Ap(5)A induces CaMKII activation. In addition, cerebellar astrocytes express a specific Ap(5)A receptor coupled to ERK activation. Ap(5)A engaged to MAPK cascade by a mechanism that was insensitive to pertussis toxin and required the involvement of src and ras proteins. Diadenosine polyphosphates, acting on their specific receptors and/or ATP receptors, can also interact with other neurotransmitter systems. This broad range of actions and interactions open a promising perspective for some relevant physiological roles for the dinucleotides. However, the physiological significance of these compounds in the CNS is still to be determined.

Adenosine Triphosphate↗

PubMed2001

Presence of diadenosine polyphosphates in human tears.

Diadenosine polyphosphates are naturally occurring substances that facilitate tear secretion. The occurrence of these dinucleotides in human tears has been established and quantified by an HPLC technique and phosphodiesterase treatment. The concentration of these compounds found in tears was 2.0+/-2.2 nM for diadenosine triphosphate (Ap3A), 108.0+/-18.3 nM for diadenosine tetraphosphate (Ap4A) and 37.0+/-6.2 nM for diadenosine pentaphosphate (Ap5A). When subjects were treated with topical ocular anaesthesia, the concentrations of Ap3A, Ap4A and Ap5A changed to 1.5+/-1.7 nM, 189.3+/-19.5 nM and 112.6+/-12.3 nM, respectively. Ap4A and Ap5A increased tear secretion in rabbits, the effect presenting an EC50 value of 19.0+/-1.2 ng/microl and 11.4+/-1.3 ng/microl respectively. In conclusion, diadenosine polyphosphates are released from the corneal epithelium, they stimulate tear production and therefore they may be considered as physiological modulators of tear secretion.

Animals↗

PubMed1990

Effect of angiotensin II and III on inositol polyphosphate production in differentiated NG108-15 hybrid cells.

Neuroblastoma x glioma hybrid cells (NG108-15), differentiated by treatment with 1.5% dimethyl sulfoxide (DMSO) and 0.5% fetal bovine serum, were used to measure the effect of angiotensin II and III (ANG II and ANG III) on the generation of inositol polyphosphates. ANG II increased the synthesis of inositol monophosphates (IP1), inositol diphosphates (IP2), and inositol trisphosphates (IP3) with maximal responses observed at 300, 120, and 30 sec, respectively. The percent increases above basal values at the maximal responses were 140% +/- 9% (IP1), 142% +/- 4% (IP2), and 132% +/- 4% (IP3). This effect was not attenuated by pretreatment of the cells with pertussis toxin. Furthermore, both ANG II and ANG III increased the production of inositol polyphosphates in a dose-dependent manner with ED50 values of 145 nM and 11 nM, respectively. We conclude that differentiated NG108-15 cells express an ANG III selective receptor that mediates phosphatidylinositol breakdown through a pertussis toxin insensitive G-protein.

Angiotensin II↗

PubMed1986

Two phases of inositol polyphosphate and diacylglycerol production at fertilisation.

[3H]Inositol and [3H]arachidonic acid were used to label polyphosphoinositide phospholipids in sea urchin eggs. Both [3H]inositol polyphosphate (InsP3) and [3H]diacylglycerol (DAG) increase at fertilisation. An early increase in InsP3 occurs as the sperm-induced calcium transient crosses the egg and exocytosis occurs; a later increase in InsP3 as calcium declines and the protein kinase C-dependent Na/H antiporter causes the cytoplasmic pH in increase. These results support suggestions that a calcium-induced hydrolysis of phosphatidylinositol bisphosphate occurs at fertilisation, that the production of diacylglycerol may be essential for exocytosis and that diacylglycerol production at fertilisation stimulates the Na/H antiporter. The increase in [3H]inositol polyphosphate as calcium declines indicates that this second messenger may have some function later in the cell cycle.

Animals↗

PubMed1990

Firefly luciferase synthesizes P1,P4-bis(5'-adenosyl)tetraphosphate (Ap4A) and other dinucleoside polyphosphates.

The synthesis of P1,P4-bis(5'-adenosyl)tetraphosphate (Ap4A) has been considered, for a long time, to be catalyzed mainly by some aminoacyl-tRNA synthetases [Brevet et al. (1989) Proc. Natl. Acad. Sci. USA 86, 8275-8279]. Recently, yeast Ap4A phosphorylase, acting in reverse (Guranowski et al. (1988) Biochemistry 27, 2959-2964), was shown to synthesize Ap4A, too. In the case of the synthetases, the intermediate complex E-aminoacyl-AMP may serve as donor of AMP to ATP, yielding Ap4A. Here we demonstrate that firefly luciferase (EC 1.13.12.7) which forms the E-luciferin-AMP intermediate also synthesizes Ap4A as well as other dinucleoside polyphosphates. We suggest moreover that: other enzymes (mainly synthetases and some transferases), which catalyze the transfer of a nucleotidyl moiety, via nucleotidyl-containing intermediates and releasing PPi may produce dinucleoside polyphosphates.

Dinucleoside Phosphates↗

PubMed1990

Proton magnetic resonance spectroscopic analysis of diadenosine 5',5"'-polyphosphates.

Certain diadenosine 5',5"'-polyphosphates are potent inhibitors of ADP stimulated platelet aggregation, acting possibly via competitive ADP-receptor binding. 1H NMR studies of a series of such compounds where the number of phosphate groups between adenosine groups was varied from 2 to 6 were performed to analyze possible preferred solution conformations and to define structure-activity relations. Relative to mononucleotides ADP and ATP, chemical shifts of adenosine proton resonances in diadenosine polyphosphate analogs are upfield shifted suggesting base stacking. This effect is greatest for AP2A and AP3A. Coupling constants of ribose ring proton resonances support the idea of an anti-base-ribose ring conformation, and 3JH5'-P values suggest a preferred gauche H-C-O-P structure. In all cases, NMR parameters for AP2A are near-limiting values for a static base stacked conformation. Increasing the number of phosphate groups between adenosine moieties tends to weaken this interaction.

Adenine Nucleotides↗

PubMed1992

Determination of inositol polyphosphates from human T-lymphocyte cell lines by anion-exchange high-performance liquid chromatography and post-column derivatization.

The intracellular amounts of several inositol tris-, tetrakis- and pentakisphosphates and inositol hexakisphosphate were determined in resting and stimulated cells from human T-lymphocyte lines. The inositol polyphosphates were separated by anion-exchange high-performance liquid chromatography and were detected on-line by a recently developed post-column dye system. In the human T-lymphocyte cell line Jurkat, basal intracellular concentrations ranged between 25 +/- 10 pmol per 10(9) cells for inositol 1,4,5-trisphosphate to 6380 +/- 355 pmol per 10(9) cells for inositol hexakisphosphate. Similar basal concentrations were observed in the human T-lymphocyte cell line HPB.ALL, with the exception that inositol hexakisphosphate was approximately 665 +/- 10 pmol per 10(9) cells. Stimulation of the human T-lymphocyte cell line Jurkat via the T-cell receptor by a monoclonal antibody directed against the T-cell receptor-CD3 complex induced time-dependent changes in the intracellular concentrations of multiple inositol polyphosphate isomers, including inositol 1,3,4-trisphosphate, inositol 1,3,4,5-tetrakisphosphate, inositol 1,3,4,6-tetrakisphosphate, an as yet unidentified inositol tetrakisphosphate isomer, inositol 1,3,4,5,6-pentakisphosphate, inositol 1,2,3,4,6-pentakisphosphate and DL-inositol 1,2,4,5,6-pentakisphosphate. Inositol 1,4,5-trisphosphate increased only transiently after 5 min, whereas DL-inositol 1,4,5,6-tetrakisphosphate (determined as the enantiomeric mixture) increased after 20 min.

Anions↗

PubMed1982

The binding of simian virus 40 large T antigen to the polyphosphate backbone of nucleic acids.

Simian virus 40 (SV40) large tumor antigen (T antigen), a phosphoprotein found in nuclei of SV40-infected and -transformed cells, binds nonspecifically to DNA. To study this mechanism the binding properties of T antigen to double-stranded (ds) and single-stranded (ss) DNA-cellulose as well as to phosphocellulose were compared. After incubation of [35S] methionine or [3H] leucine/[32 P] phosphate radioactively-labeled cell extracts at different pH values (6.0, 7.3, 9.0) with DNA- or phosphocellulose, bound and unbound species of T antigen were purified and analyzed by SDS-polyacrylamide gel electrophoresis for both the yield and the possible correlation with protein phosphorylation. T antigens bound with comparable affinities to ds- and ss-DNA-cellulose and phosphocellulose. These results suggest the binding of T antigen to the polyphosphate backbone of DNA as a molecular mechanism for its nonspecific binding. The evidence for this observation was supported by blocking the binding of T antigen to DNA-cellulose by divalent cations (Ca2+, Mg2+). 3H/32P ratios of T antigen obtained by double-labeling cells for various times imply that higher phosphorylated forms of T antigen bound more strongly to ds- and ss-DNA as well as to phosphocellulose. Thus, in the presence of cellular proteins and other components the binding activity of T antigen to the polyphosphate backbone of DNA seems to be positively correlated with its phosphorylation. These observations are consistent with the hypothesis that the binding affinities of SV40 T antigen to host cell DNA may be regulated by its phosphorylation.

Antigens, Viral↗

PubMed1984

Polyphosphate-mediated protection from cellular intoxication with Clostridium difficile toxin B.

The influence of polyphosphorylated compounds on intoxication of human lung fibroblasts with Clostridium difficile toxin B was studied. ATP, as well as other nucleoside di-, tri-, and tetraphosphates, inorganic polyphosphates and polyphosphorylated sugars, caused a dose-dependent (1-5 mM range) delay in the appearance of the cytopathogenic effect. With a longer phosphate chain, the delay was more pronounced, although the cytopathogenic effect always developed finally, reaching the level of the control within 20 h. Toxin preparations contained one fraction of molecules able to bind ATP, besides one non-binding fraction. The protective effect of ATP did not depend on its energy producing ability. Neither was the protective effect due to an inactivation of the toxin per se, or to an interference with binding of the toxin to the cells. ATP was protective even upon addition 10 min after the toxin binding step. In the presence of ATP, the toxin remained accessible to neutralization with antitoxin. In analogy with the P-site on diphtheria toxin, we postulate that C. difficile toxin B contains a polyphosphate-binding site. This site is separate from the receptor-binding site, but involved in the interaction of toxin B with the cell surface shortly after the binding step.

Adenosine Triphosphate↗

PubMed1993

Amphetamine-induced release of diadenosine polyphosphates--Ap4A and Ap5A--from caudate putamen of conscious rat.

The release of diadenosine polyphosphates--diadenosine tetraphosphate (Ap4A) and diadenosine pentaphosphate (Ap5A)--was measured by intracerebral push-pull perfusion in conscious rats after systemic amphetamine injection. Samples were collected from the caudate putamen, and nucleotide compounds were analyzed by HPLC. The presence of Ap4A and Ap5A was demonstrated by their retention times and phosphodiesterase digestion. Dinucleotides were not detectable before amphetamine injection (5 mg/kg). The maximal levels were reached 20 min after the injection with values of 12.9 +/- 0.9 and 11.5 +/- 0.9 pmol/fraction for Ap4A and Ap5A, respectively. A slow and progressive decrease in their concentration followed. This study shows for the first time the amphetamine-induced release of diadenosine polyphosphates in conscious rats, and a role for Ap4A and Ap5A in the central nervous system is therefore suggested.

Adenine Nucleotides↗

PubMed1994

Possible functional role of diadenosine polyphosphates: negative feedback for excitation in hippocampus.

Diadenosine polyphosphates (Ap4A and Ap5A) are present in secretory granules of chromaffin cells as well as in the rat brain synaptic terminals. Their contribution to the exocytosis of the total synaptosomal content is considerable, ranging from 7% to 12%. Ap4A and Ap5A are released from synaptosomes in a Ca(2+)-dependent manner. There are indications on the high affinity of diadenosine polyphosphates to P2 receptors, but their action on P1 receptors remains unclear. Here we report that both substances induce a blocking action on excitatory synaptic transmission in the rat hippocampus. This action is elicited via the A1 (subclass of P1) receptors and differs in some respects from the action of adenosine.

Animals↗

PubMed1996

Diadenosine polyphosphates selectively potentiate N-type Ca2+ channels in rat central neurons.

The action of diadenosine polyphosphates on Ca2+ channels was studied in two preparations: isolated hippocampal neurons and synaptosomes, both from the rat brain. High-voltage-activated Ca2+ channels were recorded in freshly isolated CA3 neurons using a whole-cell patch-clamp technique. Current-voltage relationships were measured in the control and after incubation in 5 microM diadenosine pentaphosphate. In the majority of tested pyramidal neurons, the latter procedure led to a reversible increase in the high-voltage-activated current through Ca2+ channels when measured at the holding potential of -100 mV but not at -40 mV. In experiments on synaptosomes from the whole brain, diadenosine pentaphosphate taken at a concentration of 100 microM increased the intrasynaptosomal calcium level measured by means of spectrofluorimetry for 26 +/- 1.8 nM (by 24 +/- 2%). Nifedipine failed to block this effect both in synaptosomes and hippocampal neurons. Potentiation of the current through Ca2+ channels in hippocampal neurons as well as the increase in intrasynaptosomal Ca2+ were irreversibly blocked by 5 microM omega-conotoxin, but not by 200 nM omega-Agatoxin-IVA. These data indicate that diadenosine polyphosphates enhance the activity of N-type Ca2+ channels in many central neurons of the rat brain.

Adenosine Triphosphate↗

PubMed1993

Cloning, sequence and characterization of the polyphosphate kinase-encoding gene (ppk) of Klebsiella aerogenes.

Polyphosphate kinase (PPK) catalyzes the formation of polyphosphate (polyP). The PPK-encoding gene (ppk) has been cloned from Klebsiella aerogenes ATCC9621. The gene possessed an open reading frame of 2055 bp capable of encoding a putative polypeptide with a deduced M(r) of 80,157. This polypeptide showed 93% similarity to the Escherichia coli PPK. The nucleotide sequence of the promoter region of K. aerogenes ppk differed from that of the previously sequenced E. coli ppk. A putative pho box sequence was found in the promoter region of K. aerogenes ppk. The expression of lacZ from the ppk promoter was increased in E. coli MV1184 under conditions of phosphate (Pi) limitation, but not in E. coli ANCS3 (phoB-), indicating that the ppk promoter is regulated by the phoB product. Increased levels of specific PPK activity were shown by expressing the cloned ppk at high levels, resulting in increased accumulation of polyP in E. coli.

Amino Acid Sequence↗

PubMed1991

Reversed-phase high-performance liquid chromatography of dinucleoside polyphosphates.

The reversed-phase high-performance liquid chromatographic separation of purine dinucleoside polyphosphates on octadecyl- and phenyl-bonded silica packings using phosphate-based eluents was studied. The effects of pH, ionic strength and the content of the organic modifiers methanol and acetonitrile in the mobile phase on the retention and other chromatographic parameters are reported. The data obtained were used to establish an isocratic assay for diguanosine and diadenosine polyphosphates.

Adrenal Medulla↗