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PubMed1994

Inactivation of calcium ion-regulating inositol polyphosphate second messengers is impaired in subpopulations of human leukemia cells.

Inositol 1,4,5-triphosphate (IP3) and inositol 1,3,4,5-tetrakisphosphate (IP4) are calcium-regulating second messenger molecules generated following the binding of a wide range of hormones and growth factors to their receptors. The actions of these messengers, which play important roles in the regulation of cell proliferation as well as in other signaling pathways, are terminated by the action of a 5-phosphomonoesterase (5-PME) enzyme. We have assayed this enzyme in normal and malignant hemopoietic cells. Extracts from normal bone marrow cells and peripheral blood mononuclear cells (PBMNC) degraded [3H]IP3 at rates of 74.5 (+/- 3.4) and 84.5 (+/- 7.9) pmol/min/micrograms protein, respectively. PME activity in 10/13 (77%) acute lymphoblastic leukemia samples were significantly below the normal range and the enzyme was completely undetectable in three (23%) of these. Enzyme activity in 8/9 (89%) chronic lymphocytic leukemia samples were below the normal range, being undetectable in three of these (33%). Nine of 24 (38%) acute myeloid leukemia samples contained low 5-PME levels, which was undetectable in one sample. Reduced 5-PME activity was detected in 2/7 (28%) of chronic granulocytic leukemia samples. The data here are consistent with the hypothesis that a reduced rate of degradation of IP3 and IP4 in some leukemia cells may result in the aberrant operation of signaling pathways, possibly including those involved in the control of cell proliferation.

Adolescent↗
PubMed1997

Disruption of three phosphatidylinositol-polyphosphate 5-phosphatase genes from Saccharomyces cerevisiae results in pleiotropic abnormalities of vacuole morphology, cell shape, and osmohomeostasis.

As a result of the genome sequencing project in Saccharomyces cerevisiae, three open reading frames were found in the yeast genome that contain sequences with strong homology to all the domains conserved among the four mammalian phosphatidylinositol-phosphate 5-phosphatases: inpp5bp, ocrl1p, synaptojanin, and ship. In addition, all three yeast gene products shared with synaptojanin regions of homology to the SAC1 gene of yeast. Disruption of each of these genes singly and in pairs produced mutant strains that were viable but demonstrated variable phenotypes of abnormal vacuolar and plasma membrane morphology as well as increased sensitivity to osmotic stress. Total phosphatidylinositol-(4,5)-bisphosphate 5-phosphatase activity was reduced to varying degrees in each of the strains. No defect in carboxypeptidase Y sorting was seen in a processing and targeting assay. Abnormal actin cytoskeleton morphology was present in some of the strains carrying mutations in two of the genes.

Amino Acid Sequence↗
PubMed1995

Purification and characterization of two exopolyphosphatases from the marine sponge Tethya lyncurium.

Two exopolyphosphatases (exopolyphosphatase I and II; EC 3.6.1.11) which release orthophosphate from inorganic polyphosphates have been detected and purified for the first time from a marine sponge. Tethya lyncurium. Exopolyphosphatase I has a molecular mass of 45 kDa, a pH optimum of 5.0 and does not require divalent cations for activity, while exopolyphosphatase II has a molecular mass of 70 kDa, a pH optimum of 7.5 and displays optimal activity in the presence of Mg2+ ions. Final purification of the enzymes could be achieved by affinity chromatography on polyphosphate-modified zirconia. The mode of action of both enzymes was found to be processive. Orthophosphate is the sole product formed by exopolyphosphatase I, while degradation of linear polyphosphates by exopolyphosphatase II occurs to pyrophosphate as end product, which is hydrolyzed, if at all, only very slowly. Significant amounts of polyphosphate (approximately 30 micrograms/g wet weight) were found to be present in the sponge organism. Polyphosphate is shown to inhibit the formation of ATP by adenylate kinase activity present in T. lyncurium extracts in a competitive manner. The inhibitory effect of long-chain polyphosphates was higher than that of short-chain polyphosphate, suggesting a potential role of polyphosphate metabolism in regulating intracellular concentrations of adenylate nucleotides.

Acid Anhydride Hydrolases↗
PubMed2004

Endogenous diadenosine tetraphosphate, diadenosine pentaphosphate, and diadenosine hexaphosphate in human myocardial tissue.

Diadenosine polyphosphates have been characterized as extracellular mediators controlling numerous physiological effects. In this study, diadenosine tetraphosphate, diadenosine pentaphosphate, and diadenosine hexaphosphate were isolated and identified in human myocardial tissue. Human myocardial tissue was homogenized and fractionated by affinity chromatography, displacement chromatography, anion-exchange chromatography, and reversed-phase chromatography. In fractions purified to homogeneity, diadenosine tetraphosphate, diadenosine pentaphosphate, and diadenosine hexaphosphate were revealed by matrix-assisted laser desorption/ionization mass spectrometry and ultraviolet spectroscopy. These diadenosine polyphosphates were further identified by enzymatic analysis, which demonstrated an interconnection of the phosphate groups with the adenosines in the 5' positions of the riboses. Furthermore, diadenosine tetraphosphate, diadenosine pentaphosphate, and diadenosine hexaphosphate were found in human cardiac-specific granules, and the amount of diadenosine tetraphosphate, diadenosine pentaphosphate, and diadenosine hexaphosphate was estimated in the range of approximately 500 micromol/L. In conclusion, the experiments show that the diadenosine polyphosphates with 2 and 3 phosphate groups occur in human myocardial tissue, and so do the diadenosine polyphosphates with 4 to 6 phosphate groups. After being released by cholinergic stimulation, which is known to affect diadenosine polyphosphate release from secretory granules, diadenosine tetraphosphate, diadenosine pentaphosphate, and diadenosine hexaphosphate activate P2X purinoceptors in vascular smooth muscle; hence, they can act as vasoconstrictors. It may be inferred that the differential action of both predominantly vasodilator and vasoconstrictor diadenosine polyphosphates allow a fine-tuning of myocardial blood flow by locally released diadenosine polyphosphates.

Cholinergic Agents↗
PubMed1975

Technetium-99m-methylene diphosphonate--a superior agent for skeletal imaging: comparison with other technetium complexes.

Methylene diphosphonate (MDP) was formulated as a complex of 99mTc for skeletal imaging. This agent was compared with three other bone-seeking technetium agents: ethane-1-hydroxy-1, 1-diphosphonate (EHDP), pyrophosphate, and polyphosphate. In tissue radioassay experiments in rodents, the technetium complexes of MDP and EHDP were similar, but skeletal concentration with both of these agents was higher than that with pyrophosphate or polyphosphate. The total-body retention of MDP and EHDP complexed with 95mTc was studied in beagle dogs for 35 days by excretion measurements and total-body counting and compared with polyphosphate and pertechnetate. The long-term retention was greater for MDP. The 5-day cumulative fecal excretion of 95mTc was low when administered as EHDP or polyphosphate complexes and negligible when administered as MDP complex. In six human volunteers the blood clearance of 99mTc-mdp was similar to that of 18F and significantly faster than that of 99mTc-EHDP. Pyrophosphate cleared from the blood much faster than polyphosphate but slower than the diphosphonates. The urinary excretion of the MDP complex was greater than for EHDP within the first 2-3 hr after injection. The 24-hr urinary excretion of pyrophosphate and polyphosphate complexes was not as complete as for the diphosphonates. All four 99mTc complexes proved satisfactory for clinical imaging studies. The MDP complex produced images of superior quality as early as 2 hr after administration, attributable to its more rapid clearance from the blood and soft tissues. On the contrary, a longer interval of 3-4 hr after injection was usually needed for 99mTc-EHDP; pyrophosphate and polyphosphate complexes regularly required a waiting period of 4 hr. Comparitive radiation dose estimates were made based on the available biologic distribution data for these 99mTc skeletal-localizing agents.

Animals↗
PubMed1990

31P NMR studies on the effect of phosphite on Phytophthora palmivora.

31P NMR spectra were obtained from perchloric acid (PCA) and KOH extracts of Phytophthora palmivora mycelium. Signals indicating the presence of large amounts of short-chain polyphosphate were observed in the spectra of PCA extracts of mycelia grown under both low (0.1 mM) and high (10 mM) phosphate conditions. The mean chain length of polyphosphate was calculated from the relative areas of signals arising from terminal and internal P nuclei in the polyphosphate chain. The small amount of polyphosphate evident in the KOH extract had an average chain length similar to PCA-soluble polyphosphate. 32P tracer studies indicated that phosphorus in the PCA fraction accounted for between 50 and 60% of total phosphorus, the bulk of the remainder being divided between the lipid and KOH extracts. The presence of the fungicide phosphorous acid markedly reduced the average chain length of acid-soluble polyphosphate. This reduction occurred both under low-phosphate conditions, in which treatment with phosphorous acid retards growth, and under high-phosphate conditions, in which no significant growth retardation is observed. Treatment with phosphorous acid perturbed phosphorus distribution and lipid composition under low-phosphate conditions.

Chytridiomycota↗
PubMed1979

Regulation of phosphate accumulation in the unicellular cyanobacterium Synechococcus.

The phosphorus contents of acid-soluble pools, lipid, ribonucleic acid, and acid-insoluble polyphosphate were lowered in Synechococcus in proportion to the reduction in growth rate in phosphate-limited but not in nitrate-limited continuous culture. Phosphorus in these cell fractions was lost proportionately during progressive phosphate starvation of batch cultures. Acid-insoluble polyphosphate was always present in all cultural conditions to about 10% of total cell phosphorus and did not turn over during balanced exponential growth. Extensive polyphosphate formation occurred transiently when phosphate was given to cells which had been phosphate limited. This material was broken down after 8 h even in the presence of excess external orthophosphate, and its phosphorus was transferred into other cell fractions, notably ribonucleic acid. Phosphate uptake kinetics indicated an invariant apparent K(m) of about 0.5 muM, but V(max) was 40 to 50 times greater in cells from phosphate-limited cultures than in cells from nitrate-limited or balanced batch cultures. Over 90% of the phosphate taken up within the first 30 s at 15 degrees C was recovered as orthophosphate. The uptake process is highly specific, since neither phosphate entry nor growth was affected by a 100-fold excess of arsenate. The activity of polyphosphate synthetase in cell extracts increased at least 20-fold during phosphate starvation or in phosphate-restricted growth, but polyphosphatase activity was little changed by different growth conditions. The findings suggest that derepression of the phosphate transport and polyphosphate-synthesizing systems as well as alkaline phosphatase occurs in phosphate shortage, but that the breakdown of polyphosphate in this organism is regulated by modulation of existing enzyme activity.

Biological Transport↗
PubMed1989

Phosphorus-31 and Nitrogen- 14 NMR Studies of the Uptake of Phosphorus and Nitrogen Compounds in the Marine Macroalgae Ulva lactuca.

Cytoplasmic phosphomonoesters and inorganic phosphate, as well as vacuolar inorganic phosphate and polyphosphates, gave rise to the major peaks in (31)P nuclear magnetic resonance (NMR) spectra of the marine macroalgae Enteromorpha sp., Ceramium sp., and Ulva lactuca which were collected from the sea. In contrast, NMR-visible polyphosphates were lacking in Pylaiella sp. and intracellular vacuolar phosphate seemed to act as the main phosphorus store in this organism. In laboratory experiments, polyphosphates decreased in growing U. lactuca which was cultivated in continuous light under phosphate-deficient conditions. In contrast, the same organism cultivated in seawater with added phosphate and ammonium, accumulated phosphate mainly in the form of polyphosphates. When nitrate was provided as the only nitrogen source, accumulation of polyphosphates in the algae decreased with increasing external nitrate concentration. From the chemical shift of the cytoplasmic Pi peak, the cytoplasmic pH of superfused preparations of Ulva was estimated at 7.2. The vacuolar pH, determined from the chemical shifts of the vacuolar Pi and the terminal polyphosphate peaks, was between 5.5 and 6.0. The intracellular nitrate and ammonium levels in U. lactuca were determined by (14)N NMR. Both nitrogen sources were taken up and stored intracellularly; however, the uptake of ammonium was much faster than that of nitrate.

Journal Article↗
PubMed1988

Role of Cations in Accumulation and Release of Phosphate by Acinetobacter Strain 210A.

Cells of the strictly aerobic Acinetobacter strain 210A, containing aerobically large amounts of polyphosphate (100 mg of phosphorus per g [dry weight] of biomass), released in the absence of oxygen 1.49 mmol of P(i), 0.77 meq of Mg, 0.48 meq of K, 0.02 meq of Ca, and 0.14 meq of NH(4) per g (dry weight) of biomass. The drop in pH during this anaerobic phase was caused by the release of 1.8 protons per PO(4) molecule. Cells of Acinetobacter strain 132, which do not accumulate polyphosphate aerobically, released only 0.33 mmol of P(i) and 0.13 meq of Mg per g (dry weight) of biomass but released K in amounts comparable to those released by strain 210A. Stationary-phase cultures of Acinetobacter strain 210A, in which polyphosphate could not be detected by Neisser staining, aerobically took up phosphate simultaneously with Mg, the most important counterion in polyphosphate. In the absence of dissolved phosphate in the medium, no Mg was taken up. Cells containing polyphosphate granules were able to grow in a Mg-free medium, whereas cells without these granules were not. Mg was not essential as a counterion because it could be replaced by Ca. The presence of small amounts of K was essential for polyphosphate formation in cells of strain 210A. During continuous cultivation under K limitation, cells of Acinetobacter strain 210A contained only 14 mg of phosphorus per g (dry weight) of biomass, whereas this element was accumulated in amounts of 59 mg/g under substrate limitation and 41 mg/g under Mg limitation. For phosphate uptake in activated sludge, the presence of K seemed to be crucial.

Journal Article↗
PubMedDate not supplied

Phosphate glass as a phosphate source in high cell density Escherichia coli fermentations.

Polyphosphate glass (sodium hexametaphosphate, sodium polyphosphate, glassy) was identified and tested as a source of phosphate that supports growth of recombinant Escherichia coli to cell densities over 110 g dry wt/L. Polyphosphate glasses cost no more than sodium and potassium phosphates, are more soluble than any other inorganic phosphate source, and do not form metallophosphate precipitates when mixed with other nutrients in proportions found in fermentation medias. Using a typical fermentation medium, 40% higher cell densities were obtained using polyphosphate glass rather than orthophosphate. Polyphosphate glasses will allow more flexibility in designing and executing high cell density fermentations.

Cell Division↗