ABSTRACT
A wide variety of ceils polymerize inorganic phosphate into long polyphosphate chains. Polyphosphates have been detected in eubacteria, archaebacteria, fungi, algae, mosses, protozoa, insects, plants, and animal tissues. In vivo nuclear magnetic resonance (NMR) observation selects mobile, soluble pools of polyphosphate. Polyphosphate pools decrease or disappear under stressful conditions and act as an energy reserve. Yeast cells hydrolyze polyphosphate to pyrophosphate when the external pH is adjusted to 8 or 9. In yeast the location of polyphosphate pools other than vacuoles appears to depend on the strain. U022+ and Eu3+ bind reversibly to the exterior of Saccharomyces fragilis cells and decrease the intensity of the polyphosphates,22 suggesting that some polyphosphate exists outside the plasma membrane. A large number of enzymes have been identified in polyphosphate synthesis and degradation. Interconversions occur among polyphosphate and P1, ATP, ADP, AMP, glucose-6-phosphate, NADP+, and 1,3-diphosphoglycerate.
