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PubMed1975

Polyphosphate levels in nongrowing cells of Saccharomyces mellis as determined by magnesium ion and the phenomenon of "Uberkompensation".

Magnesium ion enhances the maximum amount of polyphosphate that resting phosphate-starved cells of Saccharomyces mellis can store by increasing the length of time the cells will continue assimilating phosphate. The divalent cation has no effect on the rate of formation of polymer. As much as 12 times more polyphosphate is formed in cells incubated in reaction mixtures containing 0.3 M MgCl2 than in the absence of Mg2+. Potassium ion also has an influence on the amount of polyphosphate that phosphate-starved cells can accumulate but the degree of stimulation is not very large. Mg2+ and K+ have no effect on polyphosphate formation or storage in phosphate-satiated cells. Apparently, then, there are two systems for polyphosphate accumulation in S. mellis. Each system is stable in nondividing cells. The one present in phosphate-starved cells seems to be repressible by growth of the organism in media containing orthophosphate. The shift from the derepressed state to the repressed state, or vice versa, occurs only in exponentially dividing cells in appropriate media with 100% of the cells in the new physiological state by the time the cell mass has doubled. It is suggested that the word to describe the phenomenon of the accumulation of higher amounts of polyphosphate in phosphate-starved cells than the steady-state level of phosphate-satiated cells be changed from "uberkompensation" to "magnesium ubertriebung," or "magnesium enhancement."

Cell Division↗
PubMed1998

Effects of diadenosine polyphosphates on systemic and regional hemodynamics in anesthetized rats.

Diadenosine polyphosphates (Ap4A, Ap5A, Ap6A) induce vasodilatation or vasoconstriction in various isolated vessels and influence central and peripheral hemodynamics. The influence of diadenosine polyphosphates on hemodynamics was studied in anesthetized rats in vivo. Mean arterial blood pressure (MABP) and heart rate (HR) measured in the carotid artery decreased with Ap4A, Ap5A, and Ap6A. Renal blood flow (RBF), femoral blood flow (FBF) and cardiac output (CO) were evaluated by an ultrasonic transit-time method. Renal superficial blood flow (RSBF) was measured by laser Doppler flowmetry. CO, RBF and RSBF were decreased initially by all three diadenosine polyphosphates. FBF was also slightly decreased. Total peripheral (TPR), renal (RVR) and femoral (FVR) vascular resistances were calculated. TPR was transiently increased by the dinucleotides following by a decrease. RVR and, to a lesser extent, FVR were also increased. These data show that diadenosine polyphosphates have effects on both the heart and the peripheral blood vessels. The effects on the heart and MABP were dominated by bradycardia and hypotension. In the kidney, diadenosine polyphosphates induced a predominant vascoconstriction. The effects on skeletal muscle blood flow were much smaller. Thus, the three diadenosine polyphosphates studied differ in the effects on heart and peripheral vessels.

Animals↗
PubMed2001

Evaluation of ppk-specified polyphosphate as a mercury remedial tool.

To evaluate the utility of polyphosphate kinase gene (ppk)-specified polyphosphate in mercury remediation, a fusion plasmid, pMK27, with ppk from Klebsiella aerogenes and mercury transport genes, merT and merP, from Pseudomonas K-62, was constructed. The transcription and translation of ppk, merT and merP were found to be mercury-inducible. The ppk-specified polyphosphate was identified in cells preinduced by Hg2+, but not in cells without mercury induction, suggesting that the synthesis of polyphosphate is regulated by merR. The hypersensitive phenotype to Hg2+, shown by bacteria with pMRD141, which contains merT and merP, was almost completely restored to its original levels when the ppk was introduced into the plasmid, suggesting that the Hg2+-toxicity was reduced by the polyphosphate, probably via chelation formation. Bacteria with pMK27 accumulated approximately 6-fold more mercury than the bacteria with cloning vector, pUC119. These results clearly demonstrate that the polyphosphate is capable of retaining mercury in the cells without taxing the cells. Based on the results obtained in the present study, the fusion plasmid pMK27 may serve as a strategy for mercury remediation.

Bacterial Proteins↗
PubMed1992

Existence and alpha 1-adrenergic stimulation of inositol polyphosphates in mammalian heart.

The concentration-response curves and the time course of the effects of phenylephrine (0.01-100 microM) on force of contraction and on inositol polyphosphates in isolated electrically stimulated perfused rat hearts (Langendorff technique) were studied. A nonradiometric high performance liquid chromatography metal dye detection technique was used to determine absolute concentration masses/changes of inositol polyphosphates in heart. Products measured after separation with high performance liquid chromatography were inositol 1,4,5-trisphosphate (1,4,5-IP3), inositol 1,3,4,5-tetrakisphosphate (1,3,4,5-IP4) and its isomer 1,3,4,6-IP4, inositol 1,3,4,5,6-pentakisphosphate (1,3,4,5,6-IP5), and inositol hexakisphosphate (IP6). 1,4,5-IP3 (significant at 10 microM) and both IP4 isomers (significant at 1 microM) increased after alpha-adrenoceptor stimulation, whereas 1,3,4,5,6-IP5 and IP6 remained unaffected. Phenylephrine had a concentration-dependent positive inotropic effect (significant at 1 microM). All effects were antagonized by the alpha 1-adrenoceptor antagonist prazosin (0.1 microM), indicating receptor-mediated effects. In a time course study 1,4,5-IP3 was the first compound to increase significantly, within 1 min after stimulation; this rise was followed by an increase in 1,3,4,5-IP4 beginning within 2 min. The increase in all other inositol polyphosphates was slower (5-10 min). The increase in the force of contraction started at 2 min. For comparison, the effects of the beta-adrenoceptor agonist isoprenaline were studied. Isoprenaline produced a positive inotropic effect similar to that of phenylephrine, but all inositol polyphosphates remained unaffected. In conclusion, for the first time the existence of 1,3,4,5,6-IP5 and IP6 was observed in the heart. However, the physiological role of these inositol polyphosphate isomers in the heart remains to be elucidated, because, from the time course, they appear to have no acute intracellular second messenger function. Increased inositol polyphosphate turnover may be involved in the mechanism(s) whereby alpha 1-adrenoceptor stimulation produces an increase in myocardial force of contraction. Because the increase in 1,4,5-IP3 precedes and that in 1,3,4,5-IP4 coincides with the increase in the force of contraction, 1,4,5-IP3 may initiate and 1,3,4,5-IP4 may maintain the positive inotropic effect of alpha 1-adrenoceptor agonists.

Animals↗
PubMed1988

Properties of inositol polyphosphate 1-phosphatase.

We recently described inositol polyphosphate 1-phosphatase, an enzyme which cleaves the 1-phosphate from inositol 1,4-bisphosphate (Ins(1,4)P2) and inositol 1,3,4-trisphosphate (Ins(1,3,4)P3) (Inhorn, R. C., and Majerus, P. W. (1987) J. Biol. Chem. 262, 15946-15952). We have now purified the enzyme to homogeneity from calf brain. The enzyme hydrolyzes 50.3 mumol of Ins(1,4)P2/min/mg protein. The enzyme has an apparent mass of 44,000 daltons as determined both by gel filtration chromatography and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggesting that it is monomeric. Lithium ions inhibit Ins(1,3,4)P3 hydrolysis uncompetitively with an apparent Ki of approximately 0.3 mM LiCl. Calcium inhibits hydrolysis of Ins(1,4)P2 and Ins(1,3,4)P3 equally, with approximately 40% inhibition occurring at 1 microM free Ca2+. Rabbit polyclonal antiserum against purified inositol polyphosphate 1-phosphatase was prepared which immunoprecipitates approximately 0.3 milliunits of activity/microliter serum (1 unit = 1 mumol of Ins(1,4)P2 hydrolyzed per min). This antiserum was used to determine the enzyme content in several bovine tissues, all of which had a similar intrinsic specific activity (i.e. approximately 0.3 milliunits/microliter antiserum). Tissues studied included brain, heart, kidney, liver, lung, parotid, spleen, testis, and thymus. Approximately 10-15% of the total inositol polyphosphate 1-phosphatase activity in calf brain homogenates remains in a particulate fraction; antiserum also binds 0.3 milliunits of membrane-associated activity/microliter antiserum. Thus, a single enzyme can account for Ins(1,4)P2 hydrolytic activity in the bovine tissues. Ins(1,3,4)P3 metabolism was also investigated in bovine tissue homogenates. Inositol polyphosphate 1-phosphatase accounts for greater than 80% of the hydrolytic activity in all tissues studied except brain, where inositol polyphosphate 4-phosphatase is the major enzyme that hydrolyzes Ins(1,3,4)P3. The apparent Km of inositol polyphosphate 1-phosphatase for Ins(1,3,4)P3 varies approximately 3-4-fold among the bovine tissues.

Animals↗
PubMed1982

[Properties of polyphosphate phosphohydrolase of the "leaky" mutant Neurospora crassa with respect to the specific enzyme].

Some properties of polyphosphate phosphohydrolase from N. crassa strain ad-6.28610a and from its mutant with a decreased polyphosphate phosphohydrolase activity were compared. It was shown that the pH optimum for both enzyme species lies within the range of 7.1-7.3; the temperature optimum is 45 degrees. The mutant polyphosphate phosphohydrolase has a V value, which is 2 times less than that of the parent strain, and possesses a higher thermal inactivation stability. The enzymes of both cultures have practically identical values of Km(app), which depend on the length of the substrate chain. Upon transition from polyphosphate n = 9 to polyphosphate n = 180 the enzyme affinity is increased. Electrophoretic separation of cell-free extract proteins in polyacrylamide gel revealed the existence of two enzyme isoforms in both strains. The electrophoretic mobility of these isoforms are identical in both cultures. Biosynthesis of polyphosphate phosphohydrolase and tripolyphosphatase of N. crassa, unlike that of bacteria, is not controlled by a system common for alkaline phosphatase.

Acid Anhydride Hydrolases↗
PubMed2006

Molecular characterization of polyphosphate (PolyP) operon from Serratia marcescens.

The polyphosphate (polyP) operon was cloned from a genomic library of Serratia marcescens KCTC 2172 by Southern hybridization using E. coli ppk gene as a probe. The polyP operon was composed of a polyphosphate promoter, polyphosphate kinase (ppk) and exopolyphosphatase (ppx). A potential CRP binding site and pho box sequence were found in the region upstream of the putative promoter in the regulatory region. The ppk gene comprises 2,063 nucleotides and encodes 686 amino acids yielding a protein with a molecular mass of 70 kDa. The ppx gene contains 1611 nucleotides and encodes 536 amino acids with a molecular 58 kDa. An E. coli strain transformed with the ppk gene had a 16-fold increased in polyphosphate kinase activity, while introduction of the ppx gene produced a 25-fold increase in polyphosphatase activity. E. coli strains transformed with ppk and ppx genes also displayed increased accumulation of polyphosphate.

Bacterial Proteins↗
PubMed1997

A novel method for determination of inorganic polyphosphates using the fluorescent dye fura-2.

A method for determining inorganic polyphosphate, which is based on the Mn(2+)-induced quenching of the fluorescence of the calcium indicator fura-2, is described. The effect of Mn2+ ions on fura-2 fluorescence is gradually abolished in the presence of increasing concentrations of polyphosphate; this allows the quantification both of synthetic polyphosphates and of the naturally occurring polymer isolated from tissues or cells. The described method has some advantages compared to conventional procedures for detection of polyphosphates based on the metachromatic effect on toluidine blue. It can be applied for the determination of pyrophosphate, tripolyphosphate and other short-chain polyphosphates not detectable by toluidine blue and it can be used for measurement both of pyrophosphatase and exopolyphosphatase activity.

Animals↗
PubMed1995

Are polyphosphates or phosphate esters prebiotic reagents?

It is widely held that there was a phosphate compound in prebiotic chemistry that played the role of adenosine triphosphate and that the first living organisms had ribose-phosphate in the backbone of their genetic material. However, there are no known efficient prebiotic synthesis of high-energy phosphates or phosphate esters. We review the occurrence of phosphates in Nature, the efficiency of the volcanic synthesis of P4O10, the efficiency of polyphosphate synthesis by heating phosphate minerals under geological conditions, and the use of high-energy organic compounds such as cyanamide or hydrogen cyanide. These are shown to be inefficient processes especially when the hydrolysis of the polyphosphates is taken into account. For example, if a whole atmosphere of methane or carbon monoxide were converted to cyanide which somehow synthesized polyphosphates quantitatively, the polyphosphate concentration in the ocean would still have been insignificant. We also attempted to find more efficient high-energy polymerizing agents by spark discharge syntheses, but without success. There may still be undiscovered robust prebiotic syntheses of polyphosphates, or mechanisms for concentrating them, but we conclude that phosphate esters may not have been constituents of the first genetic material. Phosphoanhydrides are also unlikely as prebiotic energy sources.

Apatites↗
PubMed1980

The metabolic properties of acid soluble polyphosphates in Saccharomyces cerevisiae.

Tripolyphosphate was found to be the predominant species of soluble polyphosphate in yeast. Evidence is presented which shows that under normal growth conditions tripolyphosphate had little or no turnover. The amounts of the various polyphosphates decreased as the chain length increased. Tetrapolyphosphate was shown to be synthesized more rapidly than tripolyphosphate. These observations suggest that short chain polyphosphates arise by degradation of longer chain length polyphosphates with tripolyphosphate the ultimate degradation product. During nitrogen starvation, the normal accumulation of tripolyphosphate rapidly ceased even though the cells continued normal growth for at least two hours. After the addition of L-amino acids or (NH4)2SO4 to nitrogen starved cells, there was a dramatic increase in the accumulation of tripolyphosphate and tetrapolyphosphate which occurred at the same time as the increase in growth rate. Implications of this result are discussed in terms of possible functions of polyphosphate.

Chromatography↗
PubMed1987

Preparation of standards and determination of sizes of long-chain polyphosphates by gel electrophoresis.

Procedures are presented for isolating fractions of long-chain polyphosphates which have a narrow range of sizes and for determining their chain lengths. The polyphosphates are isolated by elution from preparative polyacrylamide gels. Then, the lengths of these polymers are determined by a method of successive approximations of length from data obtained by electrophoresis on several different gels of varying polyacrylamide concentrations. Once sized, these isolated polyphosphates may be used as electrophoresis standards, making it possible to rapidly and accurately ascertain the size of other samples having unknown chain lengths. By comparison with two other procedures for sizing polyphosphates, it is shown that the method is definitely valid to a length of 450 and most likely to a length of at least 900. This electrophoresis procedure allows, for the first time, the determination of the range of sizes present and the average chain length with only 2-20 micrograms of polyphosphate.

DNA↗
PubMed1991

Glucose determination using immobilized polyphosphate glucokinase.

Polyphosphate glucokinase (EC 2.7.1.63, polyphosphate:glucose phosphotransferase) was covalently coupled to collagen-coated silica gel beads. The immobilized enzyme, as a packed-bed reactor, was used to determine glucose in serum and other samples. The method was based on a spectrophotometric measurement of NADPH produced by two consecutive reactions, similar to the hexokinase method. The described approach takes advantage of the greater stability of polyphosphate compared to that of ATP, the greater specificity of polyphosphate glucokinase versus that of hexokinase, and the reusability of the immobilized enzyme. Linearity, precision, and accuracy of the method were tested and found to be very good. The results were linear between 10 and 50 nmol of glucose in a 50-microliter sample and the coefficient of variation was less than 4% in five successive determinations. The recovery of glucose was about 100% after calibration of the method. The results of the measurements correlated well with those obtained with soluble polyphosphate glucokinase (r = 0.997, y = 1.036x - 0.016). The immobilized-enzyme reactor showed good operational stability during a month of use, losing about 12% of its initial activity.

Collagen↗
PubMed1989

Nuclear polyphosphate as a possible source of energy during the sporulation of Physarum polycephalum.

31P NMR spectroscopic analysis of the polyphosphate pool in cellular and nuclear extracts of Physarum polycephalum demonstrates that plasmodia and cysts contain inorganic polyphosphates with an average chain length of about 100 phosphates. However, only during sporulation are these high-molecular-weight polyphosphates degraded to a lower molecular weight corresponding to an average chain length of about 10 phosphates. Since polyphosphates are degraded even in the presence of a sufficiently large pool of inorganic phosphate, produced by intracellular injection, we conclude that the degradation of polyphosphates serves in supplying energy for biosynthesis during sporulation rather than in increasing the availability of phosphate.

Cell Nucleus↗
PubMed1990

Polyphosphate-hydrolysis--a protective mechanism against alkaline stress?

Different microorganisms, including yeast and algae, accumulate large amounts of polyphosphates. However, the physiological role of polyphosphates is largely unknown. In vivo 31P NMR studies, carried out in the unicellular alga, Dunaliella salina, demonstrate the cytoplasmic alkalization induces massive hydrolysis of polyphosphates, which is correlated kinetically with the recovery of cytoplasmic pH. Analysis of acid extracts of the cells indicates that long-chain polyphosphates are hydrolysed mainly to tripolyphosphate. It is suggested that the hydrolysis of polyphosphates provides a pH-stat mechanism to counterbalance alkaline stress.

Adenosine Triphosphate↗
PubMed1991

Polyphosphate metabolism in the alga Dunaliella salina studied by 31P-NMR.

Polyphosphate synthesis and the state of the intracellular polyphosphates in the unicellular green alga Dunaliella salina were studied using in vivo 31P-NMR spectroscopy. By perfusing phosphate-depleted algal cells trapped inside agarose beads with orthophosphate (Pi) containing medium, we were able to follow the process of polyphosphate synthesis in whole, living cells. The results suggest that, in Dunaliella, low molecular weight, probably cyclic, polyphosphate intermediates are synthesized from Pi, and are then condensed to high molecular weight polymers. Studies of the intracellular organization of the polyphosphates by electron microscopy and solid-state NMR techniques indicate that most of these polymers are stored in the cell in a soluble form, and not in solid-like structures.

Chlorophyta↗
PubMed2005

Inhibition of calcite crystal growth by polyphosphates.

The inhibition of calcite crystal growth by pyrophosphate (P(2)O(7)(4-)), tripolyphosphate (P(3)O(10)(5-)), hexametaphosphate (P(6)O(18)(6-)) and binary-polyphosphate blends in calcite-seeded solutions was investigated with various solution compositions using a pH-stat system. In a single polyphosphate system, tripolyphosphate was found to be the strongest inhibitor, followed by pyrophosphate and hexametaphosphate. The inhibition can be explained by the adsorption of polyphosphates on the calcite surface conforming to a simple Langmuir adsorption model. Through a detailed speciation analysis, CaP(2)O(7)(2-) and CaP(3)O(10)(3-) were found to be the primary species of pyrophosphate and tripolyphosphate responsible for adsorption of phosphate on the calcite surface, while the responsible species for hexametaphosphate could not be determined because of a lack of published stability constants. By comparing the equilibrium constants for the adsorption reaction, the inhibitory capabilities of polyphosphates are about two orders of magnitude greater than that of orthophosphate. In binary-polyphosphate systems, the inhibition of calcite crystal growth can be described by a competitive Langmuir adsorption model using the stability constants derived from single solute systems. The inhibitory behavior of commercially available phosphate blends that are marketed to prevent calcite scale formation were demonstrated to be similar to those of laboratory-prepared blends with the same chemical composition.

Adsorption↗
PubMed1997

Anti-HIV-1 activity of inorganic polyphosphates.

Human blood plasma, serum, peripheral blood mononuclear cells, and erythrocytes contain significant amounts of inorganic polyphosphates (ranging from 53 to 116 microM, in terms of phosphate residues). Here we demonstrate that at higher concentrations linear polyphosphates display cytoprotective and antiviral activity. Sodium tetrapolyphosphate and the longer polymers, with average chain lengths of 15, 34, and 91 phosphate residues, significantly inhibited human immunodeficiency virus type 1 (HIV-1) infection of cells in vitro at concentrations > or = 33.3 microg/ml (> or = 283-324 microM phosphate residues), whereas sodium tripolyphosphate was ineffective. In the tested concentration range, these compounds had no effect on cell growth. The longer-chain polyphosphates (polyphosphates with mean chain lengths of 15 and 34) but not sodium tripolyphosphate and sodium tetrapolyphosphate also inhibited HIV-1-induced syncytium formation at a concentration of 160 microg/ml (1.51-1.54 mM phosphate residues). The results obtained with the syncytium assay and by cell-virus binding experiments indicate that the anti-HIV effect of these nontoxic polyanions may be caused by binding of the compounds to both the host cell surface and the virus, thereby inhibiting adsorption of the virus. Competition experiments revealed that binding of [32P]polyphosphate to Molt-3 cells was only partially inhibited by the antibody OKT4A.

Cell Division↗
PubMed1997

Regulation of intracellular toxic metals and other cations by hydrolysis of polyphosphate.

Heavy metal tolerance in a number of microorganisms has been correlated with the presence of long-chain polymers of inorganic phosphate called polyphosphate. It has been proposed that the polyphosphate sequesters the metals, thereby reducing their effective intracellular concentration. However, recent evidence indicates that it is not only the amount of stored polyphosphate that is important for heavy metal tolerance but also the ability to degrade polyphosphate to orthophosphate. It is proposed that, in the presence of heavy metals, polyphosphate is degraded to orthophosphate by polyphosphatase and that the metal phosphates are transported out of the cell by the inorganic phosphate transport (PIT) system. Evidence supporting this hypothesis is presented.

Alkaline Phosphatase↗