Inorganic polyphosphate (poly P) is a chain of tens or many hundreds of phosphate (Pi) residues linked by high-energy phosphoanhydride bonds. Despite inorganic polyphosphate's ubiquity--found in every cell in nature and likely conserved from prebiotic times--this polymer has been given scant attention. Among the reasons for this neglect of poly P have been the lack of sensitive, definitive, and facile analytical methods to assess its concentration in biological sources and the consequent lack of demonstrably important physiological functions. This review focuses on recent advances made possible by the introduction of novel, enzymatically based assays. The isolation and ready availability of Escherichia coli polyphosphate kinase (PPK) that can convert poly P and ADP to ATP and of a yeast exopolyphosphatase that can hydrolyze poly P to Pi, provide highly specific, sensitive, and facile assays adaptable to a high-throughput format. Beyond the reagents afforded by the use of these enzymes, their genes, when identified, mutated, and overexpressed, have offered insights into the physiological functions of poly P. Most notably, studies in E. coli reveal large accumulations of poly P in cellular responses to deficiencies in an amino acid, Pi, or nitrogen or to the stresses of a nutrient downshift or high salt. The ppk mutant, lacking PPK and thus severely deficient in poly P, also fails to express RpoS (a sigma factor for RNA polymerase), the regulatory protein that governs > or = 50 genes responsible for stationary-phase adaptations to resist starvation, heat and oxidant stresses, UV irradiation, etc. Most dramatically, ppk mutants die after only a few days in stationary phase. The high degree of homology of the PPK sequence in many bacteria, including some of the major pathogenic species (e.g. Mycobacterium tuberculosis, Neisseria meningitidis, Helicobacter pylori, Vibrio cholerae, Salmonella typhimurium, Shigella flexneri, Pseudomonas aeruginosa, Bordetella pertussis, and Yersinia pestis), has prompted the knockout of their ppk gene to determine the dependence of virulence on poly P and the potential of PPK as a target for antimicrobial drugs. In yeast and mammalian cells, exo- and endopolyphosphatases have been identified and isolated, but little is known about the synthesis of poly P or its physiologic functions. Whether microbe or human, all species depend on adaptations in the stationary phase, which is truly a dynamic phase of life. Most research is focused on the early and reproductive phases of organisms, which are rather brief intervals of rapid growth. More attention needs to be given to the extensive period of maturity. Survival of microbial species depends on being able to manage in the stationary phase. In view of the universality and complexity of basic biochemical mechanisms, it would be surprising if some of the variety of poly P functions observed in microorganisms did not apply to aspects of human growth and development, to aging, and to the aberrations of disease. Of theoretical interest regarding poly P is its antiquity in prebiotic evolution, which along with its high energy and phosphate content, make it a plausible precursor to RNA, DNA, and proteins. Practical interest in poly P includes many industrial applications, among which is the microbial removal of Pi in aquatic environments.

Inorganic polyphosphate: a molecule of many functions.

The fungal vacuole: composition, function, and biogenesis.

▪ Abstract Inorganic polyphosphate (poly P) is a chain of tens or many hundreds of phosphate (Pi) residues linked by high-energy phosphoanhydride bonds. Despite inorganic polyphosphate's ubiquity—found in every cell in nature and likely conserved from prebiotic times—this polymer has been given scant attention. Among the reasons for this neglect of poly P have been the lack of sensitive, definitive, and facile analytical methods to assess its concentration in biological sources and the consequent lack of demonstrably important physiological functions. This review focuses on recent advances made possible by the introduction of novel, enzymatically based assays. The isolation and ready availability of Escherichia coli polyphosphate kinase (PPK) that can convert poly P and ADP to ATP and of a yeast exopolyphosphatase that can hydrolyze poly P to Pi, provide highly specific, sensitive, and facile assays adaptable to a high-throughput format. Beyond the reagents afforded by the use of these enzymes, their gene...

https://link.springer.com/content/pdf/10.1007%2F978-3-642-58444-2_1.pdf

Inorganic Polyphosphate: A Molecule of Many Functions

Metabolite profiling by one- and two-dimensional NMR analysis of complex mixtures

Glycogen and trehalose are the two glucose stores of yeast cells. The large variations in the cell content of these two compounds in response to different environmental changes indicate that their metabolism is controlled by complex regulatory systems. In this review we present information on the regulation of the activity of the enzymes implicated in the pathways of synthesis and degradation of glycogen and trehalose as well as on the transcriptional control of the genes encoding them. cAMP and the protein kinases Snf1 and Pho85 appear as major actors in this regulation. From a metabolic point of view, glucose-6-phosphate seems the major effector in the net synthesis of glycogen and trehalose. We discuss also the implication of the recently elucidated TOR-dependent nutrient signalling pathway in the control of the yeast glucose stores and its integration in growth and cell division. The unexpected roles of glycogen and trehalose found in the control of glycolytic flux, stress responses and energy stores for the budding process, demonstrate that their presence confers survival and reproductive advantages to the cell. The findings discussed provide for the first time a teleonomic value for the presence of two different glucose stores in the yeast cell.

Reserve carbohydrates metabolism in the yeast Saccharomyces cerevisiae

High-resolution phosphorus-31 nuclear magnetic resonance (31P NMR) spectra of wild-type and mutant strains of Saccharomyces cerevisiae were observed at a frequency of 145.7 MHz. Levels of various phosphorus metabolites were investigated upon addition of glucose under both aerobic and anaerobic conditions. Three mutant strains were isolated and their biochemical defects characterized: pfk lacked phosphofructokinase activity; pgi lacked phosphoglucose isomerase activity; and cif had no glucose catabolite repression of the fructose bisphosphatase activity. Each mutant strain was found to accumulate characteristic sugar phosphates when glucose was added to the cell suspension. In the case of the phosphofructokinase deficient mutant, the appearance of a pentose shunt metabolite was observed. 31P NMR peak assignments were made by a pH titration of the acid extract of the cells. Separate signals for terminal, penultimate, and central phosphorus atoms in intracellular polyphosphates allowed the estimation of their average molecular weight. Signals for glycero(3)phosphochline, glycero(3)phosphoserine, and glycero(3) phosphoethanolamine as well as three types of nucleotide diphosphate sugars could be observed. The intracellular pH in resting and anaerobic cells was in the range 6.5--6.8 and the level of adenosine 5'-triphosphate (ATP) low. Upon introduction of oxygen, the ATP level increased considerably and the intracellular pH reached a value of pH 7.2--7.3, irrespective of the external medium pH, indicating active proton transport in these cells. A new peak representing the inorganic phosphate of one of the cellular organelles, whose pH differed from the cytoplasmic pH, could be detected under appropriate conditions.

Lam Kb

Papers

Phosphorus-31 nuclear magnetic resonance studies of wild-type and glycolytic pathway mutants of Saccharomyces cerevisiae.