Effects of growth state and amines on cytoplasmic and vocuolar pH, phosphate and polyphosphate levels in Saccharomyces cerevisiae: a P-nuclear magnetic resonance study

The vacuoles of logarithmic and stationary stage cells were compared by ³¹P-NMR with regard to pH, orthophosphate (P_i) content and average size of polyphosphate. The vacuoles of stationary cells had lower pH higher P_i content, and polyphosphates of longer average chain lenght, although total polyphosphate content was about the same as in logarithmic cells. The lower vacuolar pH in stationary cells was the major cause of a larger cytoplasmic-vacuolar pH gradient. Addition of NH₄Cl, (NH₄)₂SO₄, methylamine or amantadine at pH 8 to cells in either stage caused an icnrease in both cytoplasmic and vacuolar pH, with little or no change in the cytoplasmic-vacuolar pH gradient. However, the administration of ammonium salts to the cells at pH 8.0 resulted in rapid hydrolysis of the intravacuolar polyphosphate to tripolyphosphate and P_i, with attendant redistribution of P_i between the vacuolar and cytoplasmic compartments.     

Effects of growth state and amines on cytoplasmic and vocuolar pH,phosphate and polyphosphate levels in Saccharomyces cerevisiae: a 31P-nuclear magnetic resonance study

The vacuoles of logarithmic and stationary stage cells were compared by ³¹P-NMR with regard to pH, orthophosphate (P_i) content and average size of polyphosphate. The vacuoles of stationary cells had lower pH higher P_i content, and polyphosphates of longer average chain lenght, although total polyphosphate content was about the same as in logarithmic cells. The lower vacuolar pH in stationary cells was the major cause of a larger cytoplasmic-vacuolar pH gradient. Addition of NH₄Cl, (NH₄)₂SO₄, methylamine or amantadine at pH 8 to cells in either stage caused an icnrease in both cytoplasmic and vacuolar pH, with little or no change in the cytoplasmic-vacuolar pH gradient. However, the administration of ammonium salts to the cells at pH 8.0 resulted in rapid hydrolysis of the intravacuolar polyphosphate to tripolyphosphate and P_i, with attendant redistribution of P_i between the vacuolar and cytoplasmic compartments.     

Studies on the polyphosphate cycle in Candida utilis

Summary Candida utilis cells were grown in continuous culture in a medium with ammonium or arginine as the nitrogen source. Arginine produced a marked change in the amount of polyphosphates and arginine in whole cells and vacuoles, as well as in the ratio of the concentrations of these substances. The specific growth rate () which in continuous culture is equivalent to the dilution rate (D), affects the amount and chain length of the polyphosphates and also the arginine content of the vacuoles and whole cells. Thus, if D is increased the amount of polyphosphates per milligram protein is increased. There is apparently a direct and linear relationship between D, the specific growth rate () and the polyphosphate content. Changes in D also affect the length of the polyphosphate chain, and the relationship is inverse. At low growth rates, two types of chain were observed, one of approximately 35 phosphate units and the other of 5 units. At high growth rates phosphorus was not stored as longchain polyphosphates.     

P-31 in-vivo NMR investigation on the function of polyphosphates as phosphate-and energysource during the regreening of the green alga Chlorella fusca

The green alga Chlorella fusca accumulates polyphosphates under conditions of nitrogen starvation while deassembling the photosynthetic apparatus. The polyphosphate content of cells regreening after resupply with nitrate under different culture conditions was investigated by P-31 in-vivo NMR spectroscopy. Neither phosphate deficiency nor anaerobiosis during the first hours of regreening inhibited the recovery of the cells. Polyphosphates were degraded during regeening. Differences in the amount of polyphosphates of phosphate supplied and deficient cells occurred only after more then 8 h. After 16 h phosphate deficient cells had still 75% of the polyphosphate content of phosphate suppled cells. In cells kept under anaerobic conditions polyphosphate degradation was much higher than in oxygen supplied cells. After 8 h they contained less than 50% of the polyphosphate content of oxygen supplied cells. These data suggest that polyphosphates serve as obligatory phosphate source during regreening and may be used as an energy source.Non standard abbreviations EDTA Ethylene diamine tetraacetic acid - FID Free induction decay - MOPSO 3-(N-morpholine)-2-hydroxy-propanesulfonic acid - NMR Nuclear magnetic resonance - PP Polyphosphates - PP₄ central phosphate groups of polyphosphates     

Control of Vertebrate Skeletal Mineralization by Polyphosphates

Background

Skeletons are formed in a wide variety of shapes, sizes, and compositions of organic and mineral components. Many invertebrate skeletons are constructed from carbonate or silicate minerals, whereas vertebrate skeletons are instead composed of a calcium phosphate mineral known as apatite. No one yet knows why the dynamic vertebrate skeleton, which is continually rebuilt, repaired, and resorbed during growth and normal remodeling, is composed of apatite. Nor is the control of bone and calcifying cartilage mineralization well understood, though it is thought to be associated with phosphate-cleaving proteins. Researchers have assumed that skeletal mineralization is also associated with non-crystalline, calcium- and phosphate-containing electron-dense granules that have been detected in vertebrate skeletal tissue prepared under non-aqueous conditions. Again, however, the role of these granules remains poorly understood. Here, we review bone and growth plate mineralization before showing that polymers of phosphate ions (polyphosphates: (PO₃ ⁻)_n) are co-located with mineralizing cartilage and resorbing bone. We propose that the electron-dense granules contain polyphosphates, and explain how these polyphosphates may play an important role in apatite biomineralization.

Principal Findings/Methodology

The enzymatic formation (condensation) and destruction (hydrolytic degradation) of polyphosphates offers a simple mechanism for enzymatic control of phosphate accumulation and the relative saturation of apatite. Under circumstances in which apatite mineral formation is undesirable, such as within cartilage tissue or during bone resorption, the production of polyphosphates reduces the free orthophosphate (PO₄ ³⁻) concentration while permitting the accumulation of a high total PO₄ ³⁻ concentration. Sequestering calcium into amorphous calcium polyphosphate complexes can reduce the concentration of free calcium. The resulting reduction of both free PO₄ ³⁻ and free calcium lowers the relative apatite saturation, preventing formation of apatite crystals. Identified in situ within resorbing bone and mineralizing cartilage by the fluorescent reporter DAPI (4′,6-diamidino-2-phenylindole), polyphosphate formation prevents apatite crystal precipitation while accumulating high local concentrations of total calcium and phosphate. When mineralization is required, tissue non-specific alkaline phosphatase, an enzyme associated with skeletal and cartilage mineralization, cleaves orthophosphates from polyphosphates. The hydrolytic degradation of polyphosphates in the calcium-polyphosphate complex increases orthophosphate and calcium concentrations and thereby favors apatite mineral formation. The correlation of alkaline phosphatase with this process may be explained by the destruction of polyphosphates in calcifying cartilage and areas of bone formation.

Conclusions/Significance

We hypothesize that polyphosphate formation and hydrolytic degradation constitute a simple mechanism for phosphate accumulation and enzymatic control of biological apatite saturation. This enzymatic control of calcified tissue mineralization may have permitted the development of a phosphate-based, mineralized endoskeleton that can be continually remodeled.     

Interrelationship of polyphosphate metabolism and levorin biosynthesis in Streptomyces levoris

The effect of inorganic phosphate on biosynthesis of the polyene antibiotic levorin by Streptomyces levoris was studied. At phosphate concentration of 4.0 mM levorin biosynthesis is repressed by 90%, resulting in an increase of ATP and a condensed inorganic polyphosphates content in the producer cells. At phosphate concentration optimal for levorin production (0.04 mM) the level of intracellular ATP sharply falls by the beginning of the steady-state phase of the producer growth and that of polyphosphates decreases 3-6-fold. The inorganic phosphate exerts different effects on polyphosphate metabolism enzymes, such as polyphosphate: D-glucose-6-phosphotransferase, polyphosphate phosphohydrolase, tripolyphosphate phosphohydrolase, pyrophosphate phosphohydrolase, alkaline and acid phosphatase. The strongest effect of phosphate excess is observed in the case of polyphosphate: D-glucose-6-phosphotransferase, whose activity decreases 2-5-fold. The activity of this enzyme was shown to be correlated with the antibiotic accumulation. The data obtained are indicative of interrelationship between the polyphosphate metabolism and levorin biosynthesis.     

Inorganic polyphosphate in the yeast <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> with a mutation disturbing the function of vacuolar ATPase

A mutation in the vma2 gene disturbing V-ATPase function in the yeast Saccharomyces cerevisiae results in a five- and threefold decrease in inorganic polyphosphate content in the stationary and active phases of growth on glucose, respectively. The average polyphosphate chain length in the mutant cells is decreased. The mutation does not prevent polyphosphate utilization during cultivation in a phosphate-deficient medium and recovery of its level on reinoculation in complete medium after phosphate deficiency. The content of short chain acid-soluble polyphosphates is recovered first. It is supposed that these polyphosphates are less dependent on the electrochemical gradient on the vacuolar membrane.     

Untersuchungen über die Raten der Polyphosphatsynthese durch die Photophosphorylierung bei Ankistrodesmus braunii

Summary Short-time experiments with ³²P-labelled phosphate and chase experiments with equally labelled cells were carried out with synchronized algae under conditions of optimum phosphate uptake. In short-time experiments, in the presence as in the absence of CO₂, orthophosphate and organic phosphates are rapidly labelled, but their time curves show saturation behaviour after 10 to 20 min. Labelling of polyphosphates proceeds at a constant rate after a short lag period of about 5 min. In equally labelled algae ³²P-labelling correspondingly decreases in orthophosphate and in organic phosphates, but increases by about the same amount in the fraction of acid-insoluble polyphosphates. In the presence of external phosphate and in the light, polyphosphates show no visible decay within the 20 min of the chase experiments.A comparison of the two kinds of experiments suggests that polyphosphates are secondary products of photophosphorylation following only after orthophosphate and organic phosphates, probably after ATP. The rates of photophosphorylation are certainly much higher than the rates of labelling in organic phosphates because of the limiting phosphate uptake. Since the polyphosphates show no decay during the time of the experiments their turnover is low and the rates of polyphosphate labelling after a phosphate starvation period, and after the short lag period, can be regarded as approximate rates of polyphosphate synthesis. These rates are lower than the rates of phosphate uptake.In young cells of the synchronous culture phosphate replenishment after a 5-h starvation requires 2 to 3 h. After replenishment or in a culture undisturbed by phosphate starvation, the rates of polyphosphate accumulation, like the rates of phosphate uptake are much lower. In the presence of CO₂ they are constant for several hours, if related to culture volume with constant cell number. Polyphosphate accumulation is proportional to phosphate uptake under these conditions amounting to about one third. In the absence of CO₂, the rates decrease after 2 to 4 h of CO₂-starvation and, like in short-time experiments a large proportion of the phosphate taken up is used for polyphosphate accumulation. The low rates of long-time experiments may represent a steady state between formation and decay of polyphosphates. Since the cells kept in the absence of CO₂ are prevented from growing they actually accumulate more polyphosphates per cell volume, per chlorophyll, and per dry weight than the cells in the presence of CO₂.The rates of polyphosphate formation are discussed with respect to their turnover in the light observed by other investigators. They are regarded to be a result of competition for ATP together with the orthophosphate pool of the cells, and of the compartmentation. The rates of polyphosphate formation are rather low compared with the probable rates of ATP formation under various conditions of photophosphorylation. Therefore, the formation of polyphosphates is regarded as a process of secondary order of magnitude in the energy metabolism of algal cells.

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Im Text verwendete Abkürzungen P₁ Trichloressigsäure lösliche Phosphate - davon P_i Orthophosphat - P_o organisches Phosphat - P_ul Hydrolyse-labiles TCE-unlösliches Phosphat - P_us Hydrolyse-stabiles TCE-unlösliches Phosphat - P_ges Gesamtphosphat, bei kurzzeitiger ³²P-Markierung Phosphataufnahme - Chl Chlorophyll     

Polyphosphate Hydrolysis within Acidic Vacuoles in Response to Amine-Induced Alkaline Stress in the Halotolerant Alga Dunaliella salina

The location and mobilization of polyphosphates in response to an amine-induced alkaline stress were studied in the halotolerant alga Dunaliella salina. The following observations suggest that polyphosphates accumulate in acidic vacuoles: (a) Accumulation of large amounts of polyphosphates is manifested as intravacuolar dense osmiophilic bodies in electron micrographs. (b) Uptake of amines into the vacuoles induces massive hydrolysis of polyphosphates, demonstrated by in vivo ³¹P-nuclear magnetic resonance, and by analysis of hydrolytic products on thin layer chromatograms. The analysis indicates that: (a) Polyphosphate hydrolysis is kinetically correlated with amine accumulation and with the recovery of cytoplasmic pH. (b) The major hydrolytic product is tripolyphosphate. (c) The peak position of the tripolyphosphate terminal phosphate in nuclear magnetic resonance spectra is progressively shifted as the cells recover, indicating that the pH inside the vacuoles increases while the pH in the cytoplasm decreases. (d) In lysed cell preparations, in which vacuoles become exposed to the external pH, mild alkalinization in the absence of amines induces polyphosphate hydrolysis to tripolyphosphates. It is suggested that amine accumulation within vacuoles activates a specific phosphatase, which hydrolyzes long-chain polyphosphates to tripolyphosphates. The hydrolysis increases the capacity of the vacuoles to sequester amines from the cytoplasm probably by releasing protons required to buffer the amine, and leads to recovery of cytoplasmic pH. Thus, polyphosphate hydrolysis provides a high-capacity buffering system that sustains amine compartmentation into vacuoles and protects cytoplasmic pH.     

Isolation and characterization of polyphosphates from the yeast cell surface

When cells of Saccharomyces fragilis are subjected to osmotic shock, they release a limited amount of inorganic polyphosphate into the medium, which represents about 10% of the total cellular content. The osmotic shock procedure causes no substantial membrane damage, as judged from the unimpaired cell viability, limited K⁺ leakage and low percentage of stained cells. It is therefore suggested that this polyphosphate fraction is localized outside the plasma membrane. The released polyphosphate fraction differs from the remaining cellular polyphosphates in two respects: the mean chain length of the shock-sensitive fraction is significantly higher than that of the total cellular polyphosphates and its metabolic turnover rate, subsequent to pulsing with [³²P]orthophosphate is much lower compared to the rest of the cellular polyphosphate. Incubation of intact cells with the anion exchange resin Dowex AG 1-X4 results in the release of high molecular weight polyphosphates. These results suggest that the osmotic shock-sensitive polyphosphate fraction has specific characteristics in both its cellular localization and metabolism.     

Preferential utilization of inorganic polyphosphate over other bioavailable phosphorus sources by the model diatoms Thalassiosira spp.

Polyphosphates and phosphomonoesters are dominant components of marine dissolved organic phosphorus (DOP). Collectively, DOP represents an important nutritional phosphorus (P) source for phytoplankton growth in the ocean, but the contribution of specific DOP sources to microbial community P demand is not fully understood. In a prior study, it was reported that inorganic polyphosphate was not bioavailable to the model diatoms Thalassiosira weissflogii and Thalassiosira pseudonana. However, in this study, we show that the previous finding was a misinterpretation based on a technical artefact of media preparation and that inorganic polyphosphate is actually widely bioavailable to Thalassiosira spp. In fact, orthophosphate, inorganic tripolyphosphate (3polyP), adenosine triphosphate (ATP) and adenosine monophosphate supported equivalent growth rates and final growth yields within each of four strains of Thalassiosira spp. However, enzyme activity assays revealed in all cultures that cell-associated hydrolysis rates of 3polyP were typically more than ~10-fold higher than degradation of ATP and the model phosphomonoester compound 4-methylumbelliferyl phosphate. These results build on prior work, which showed the preferential utilization of polyphosphates in the cell-free exudates of Thalassiosira spp., and suggest that inorganic polyphosphates may be a key bioavailable source of P for marine phytoplankton.     

Polyphosphate glucokinase from Propionibacterium shermanii. Kinetics and demonstration that the mechanism involves both processive and nonprocessive type reactions

Polyphosphate glucokinase (EC 2.7.1.63, polyphosphate glucose phosphotransferase) has been partially purified (960-fold) from Propionibacterium shermanii. Throughout the purification, the ratio of polyphosphate glucokinase activity to ATP glucokinase activity remained approximately constant at 4 to 1. It is considered that both activities are catalyzed by the same protein. The mechanism of utilization of polyphosphate by polyphosphate glucokinase was investigated using polyphosphates of limited sizes that were isolated following gel electrophoresis of commercial heterogeneous polyphosphates. The results show that with long chain polyphosphates, the reaction proceeds by a processive type mechanism, and with short polyphosphates, it is nonprocessive. The Km for polyphosphate of chain length 724 is 2 X 10(-3) microM and increases with a decrease in chain length to 3.7 X 10(-2) microM at chain length 138. Subsequently, there is a very rapid increase of Km and at chain length 30 the Km is 4.3 microM. The rapid change in Km coincides with the shift in mechanism from the processive type mechanism in which there apparently is successive phosphorylation prior to release from the enzyme to a nonprocessive process in which the polyphosphate is released from the enzyme after each transfer. During the nonprocessive process, there is preferential utilization of the longer species. The Vmax is relatively constant with shorter polyphosphates but decreases with chain lengths longer than 347. In the cell, as a consequence of the low Km, the long chain polyphosphates probably are used preferentially to phosphorylate glucose.     

P and C-NMR Studies of the Phosphorus and Carbon Metabolites in the Halotolerant Alga, Dunaliella salina

The intracellular phosphorus and carbon metabolites in the halotolerant alga Dunaliella salina adapted to different salinities were monitored in living cells by ³¹P- and ¹³C-nuclear magnetic resonance (NMR) spectroscopy. The ¹³C-NMR studies showed that the composition of the visible intracellular carbon metabolites other than glycerol is not significantly affected by the salinity of the growth medium. The T₁ relaxation rates of the ¹³C-glycerol signals in intact cells were enhanced with increasing salinity of the growth medium, in parallel to the expected increase in the intracellular viscosity due to the increase in intracellular glycerol. The ³¹P-NMR studies showed that cells adapted to the various salinities contained inorganic phosphate, phosphomonoesters, high energy phosphate compounds, and long chain polyphosphates. In addition, cells grown in media containing up to 1 molar NaCl contained tripolyphosphates. The tripolyphosphate content was also controlled by the availability of inorganic phosphate during cell growth. Phosphate-depleted D. salina contained no detectable tripolyphosphate signal. Excess phosphate, however, did not result in the appearance of tripolyphosphate in ³¹P-NMR spectra of cells adapted to high (>1.5 molar NaCl) salinites.     

Untersuchungen zum Polyphosphatstoffwechsel und der Bildung metachromatischer Granula bei Mycobacterium phlei

Summary Metachromatic granules and polyphosphate necessary for their synthesis increase rapidly in growing and resting cells of Mycobacterium phlei. The orthophosphate which the bacteria absorb, is transferred into an energy-rich bond during the oxydative phosphorylation, and for the most part utilized directly in the synthesis of the high molecular polyphosphate found in the acid-unsoluble fraction.2,4-dinitrophenol, 2,6-dichlorphenolindophenol, methylene blue, trypaflavine, potassium cyanide, o-phenanthroline, and monojodo acetic acid inhibit the absorption of O₂ and the synthesis of polyphosphates. 2,4-dinitrophenol and sodium azide exhibit no typical uncoupling effect. Fluoro-acetic acid and inhibitors of SH-groups, e.g. p-chloromercuribenzoate and mercuric chloride (sublimate), too, block the formation of granules and polyphosphates.Ribonuclease has a pronounced uncoupling effect to phosphorylation. l- and d,l-ethionine block the synthesis of proteins and nucleic acids and prevent the degradation of the polyphosphates, which starts in normally growing cultures after about 3 to 4 hours, reaching equilibrium after about 12 hours. The utilization of polyphosphates as a source of energy and phosphate in the metabolism of multiplication is discussed.

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Abkürzungen Gr Granula, Granulum - m. Gr. metachromatische Granula - P Phosphor - Ph Phosphat - PoPh Polyphosphat - NS Nucleinsäure - RNS Ribonucleinsäure - DNS Desoxyribonucleinsäure - RN'ase Ribonuclease - DN'ase Desoxyribonuclease - ATP Adenosintriphosphat - ADP Adenosindiphosphat - DPN Diphosphoryridinnucleotid - DPNH Diphosphopyridinnucleotid (reduziert) - TCE Trichloressigsäure Herrn Professor Dr. K. Mothes zu seinem 60. Geburtstag gewidmet.     

Distribution of polyphosphates in cell-compartments of Chlorella fusca as measured by 31P-NMR-spectroscopy

In suspensions of the green alga Chlorella fusca the influence of high pH and high ethylene-diamine-tetraacetic acid concentrations in the external medium, of French-press and perchloric acid extraction of the cells and of alkalization of the intracellular pH on the polyphosphate signal in ³¹P-nuclear magnetic resonance (³¹P NMR) spectra was investigated.The results show that part of the polyphosphates of asynchronous Chlorella cells are located outside the cytoplasmic membrane and complexed with divalent metal-ions. These polyphosphates are tightly bound to the cell wall and/or the cytoplasmic membrane and are not susceptible to hydrolyzation by strong acid at room temperature, in contrast to the intracytoplasmic polyphosphates.Upon alkalization of the internal pH of Chlorella cells, polyphosphates, previously not visible in the spectra become detectable by ³¹P-NMR-spectroscopy. ³¹P-NMR spectroscopic monitoring of polyphosphates during gradual alkalization of the extra-and intracellular space is proposed as a quick method for the estimation of the cellular polyphosphate content and distribution.Abbreviations CCCP Carbonylcyanide-m-chlorophenyl-hydrazone - NTP/NDP Nucleotide triphosphate/-diphosphate - PCA Perchloric acid - ³¹P-NMR ³¹P-nuclear magnetic resonance - PolyP polyphosphates - PP₁, PP₂, PP₃ terminal, second and third phosphate residue of polyphosphates, respectively - PP₄ core phosphate residues of polyphosphates     

Polyphosphate synthesis in yeast

Polyphosphate synthesis was studied in phosphate-starved cells of Saccharomyces cerevisiae and Kluyveromyces marxianus. Incubation of these yeasts for a short time with phosphate and either glucose or ethanol resulted in the formation of polyphosphate with a short chain length. With increasing incubation times, polyphosphates with longer chain lengths were formed. Polyphosphates were synthesized faster during incubation with glucose than with ethanol. Antimycin did not affect the glucose-induced polyphosphate synthesis in either yeast. Using ethanol as an energy source, antimycin A treatment blocked both polyphosphate synthesis and accumulation of orthophosphate in the yeast S. cerevisiae. However, in K. marxianus, polyphosphate synthesis and orthophosphate accumulation proceeded normally in antimycin-treated cells, suggesting that endogenous reserves were used as energy source. This was confirmed in experiments, conducted in the absence of an exogenous energy source.     

Inorganic Polyphosphates and Exopolyphosphatases in Cell Compartments of the Yeast Saccharomyces cerevisiae Under Inactivation of PPX1 and PPN1 Genes

Purified fractions of cytosol, vacuoles, nuclei, and mitochondria of Saccharomyces cerevisiae possessed inorganic polyphosphates with chain lengths characteristic of each individual compartment. The most part (80–90%) of the total polyphosphate level was found in the cytosol fractions. Inactivation of a PPX1 gene encoding ~40-kDa exopolyphosphatase substantially decreased exopolyphosphatase activities only in the cytosol and soluble mitochondrial fraction, the compartments where PPX1 activity was localized. This inactivation slightly increased the levels of polyphosphates in the cytosol and vacuoles and had no effect on polyphosphate chain lengths in all compartments. Exopolyphosphatase activities in all yeast compartments under study critically depended on the PPN1 gene encoding an endopolyphosphatase. In the single PPN1 mutant, a considerable decrease of exopolyphosphatase activity was observed in all the compartments under study. Inactivation of PPN1 decreased the polyphosphate level in the cytosol 1.4-fold and increased it 2- and 2.5-fold in mitochondria and vacuoles, respectively. This inactivation was accompanied by polyphosphate chain elongation. In nuclei, this mutation had no effect on polyphosphate level and chain length as compared with the parent strain CRY. In the double mutant of PPX1 and PPN1, no exopolyphosphatase activity was detected in the cytosol, nuclei, and mitochondria and further elongation of polyphosphates was observed in all compartments.     

Metabolism characteristics of <Emphasis Type="Italic">Chelativorans oligotrophicus</Emphasis> by two-phase growth on the mixture of EDTA and glucose

The obligate destructor of ethylene diamine tetraacetate—a culture of Chelativorans oligotrophicus LPM-4—did not grow on a medium with glucose, but it was good to use it under cultivation on a mixture with EDTA after considerable decrease of the EDTA concentration in the medium (two-phase growth). Strong inhibition of hexokinase and glucose 6-phosphate dehydrogenase in cell exracts 4 mM EDTA was revealed. Using EDTA, cells accumulated polyphosphates whose rate decreased during glucose utilization phase. High activities of polyphosphate biosynthesis ferments (adenylat kinase and polyphosphate kinase) were distinguished during the first phase of the cultivation; considerable decrease of them and increase of polyphosphate glucokinase were found during the second phase of the cultivation. This points to the possible participating of polyphosphates in glucose metabolism as a supplementary energy source.     

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.     

<Superscript>31</Superscript>P NMR study of polyphosphate levels during different growth phases of <Emphasis Type="Italic">Phycomyces blakesleeanus</Emphasis>

The changes in relative polyphosphate content, estimated as the intensity ratio of core polyphosphate signal and intracellular inorganic phosphate signal from ³¹P NMR spectra, during the growth of Phycomyces blakesleeanus are reported. The ratio increases from 16 h to 28 h of growth, the minimum occurs at 32 h, followed by sharp increase up to 36 h, and a steady decrease afterwards. The changes in the biomass during mycelium growth showed steady increases, with a stagnation period between 32 h and 36 h during which a pronounced increase in the intensity ratio of core polyphosphates to intracellular inorganic phosphate signal occurred. The reduction of growth temperature from 22°C to 18°C significantly decreased the rate and intensity of growth, but the pattern of polyphosphate changes remained unchanged. The changes of the intensity ratio of core polyphosphates to intracellular inorganic phosphate signal are linked to characteristic stages of sporangiophore development. Analysis of core polyphosphates, intracellular inorganic phosphate and β-ATP signal intensities suggest the role of polyphosphates as an energy and/or a phosphate reserves during Phycomyces development.