High molecular weight polyphosphates are well known. One derivative is the
glassy (i.e., amorphous)
Graham's salt. Crystalline high molecular weight polyphosphates include Kurrol’s salt and Maddrell’s salt (white powder practically insoluble in water). These species have the formula [NaPO3]n[NaPO3(OH)]2 where n can be as great as 2000. In terms of their structures, these polymers consist of PO3− "monomers", with the chains are terminated by protonated phosphates.
In nature High-polymeric inorganic polyphosphates were found in living organisms by L. Liberman in 1890. These compounds are linear polymers containing a few to several hundred residues of
orthophosphate linked by energy-rich
phosphoanhydride bonds. Previously, it was considered either as “
molecular fossil” or as only a phosphorus and energy source providing the survival of microorganisms under extreme conditions. These compounds are now known to also have regulatory roles, and to occur in representatives of all kingdoms of living organisms, participating in metabolic correction and control on both genetic and enzymatic levels. Polyphosphate is directly involved in the switching-over of the genetic program characteristic of the exponential growth stage of bacteria to the program of cell survival under stationary conditions, "a life in the slow lane". They participate in many regulatory mechanisms occurring in bacteria: • They participate in the induction of
rpoS, an RNA-polymerase subunit which is responsible for the expression of a large group of genes involved in adjustments to the stationary growth phase and many stressful agents. • They are important for cell motility, biofilms formation and virulence. • Polyphosphates and
exopolyphosphatases participate in the regulation of the levels of the stringent response factor, guanosine 5'-diphosphate 3'-diphosphate (ppGpp), a second messenger in bacterial cells. • Polyphosphates participate in the formation of channels across the living cell membranes. The above channels formed by polyphosphate and poly-b-hydroxybutyrate with Ca2+ are involved in the transport processes in a variety of organisms. • An important function of polyphosphate in microorganisms—prokaryotes and the lower eukaryotes—is to handle changing environmental conditions by providing phosphate and energy reserves. Polyphosphates are present in animal cells, and there are many data on its participation in the regulatory processes during development and cellular proliferation and differentiation—especially in bone tissues and brain. In humans polyphosphates are shown to play a key role in blood
coagulation. Produced and released by
platelets they activate blood coagulation
factor XII which is essential for blood clot formation. Factor XII, also called Hageman factor, initiates fibrin formation and the generation of a proinflammatory mediator,
bradykinin, that contributes to
leakage from the blood vessels and thrombosis. Bacterial-derived polyphosphates impair the host immune response during infection and targeting polyphosphates with recombinant exopolyphosphatase improves sepsis survival in mice. Inorganic polyphosphates play a crucial role in tolerance of yeast cells to toxic heavy metal cations. ==Use as food additives==