Page 137 - The Biochemistry of Inorganic Polyphosphates

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The functions of polyphosphates in higher eukaryotes 121
Nucleoid RNA polymerase,
Regulation of gene expression Activity regulation
Cytoplasm
P and energy reserve, enzyme Cell capsule
i
activity regulation
Virulence, quorum sensing, cation
sequestration

Volutin granules
Cytoplasmic membrane
P reserve, cation sequestration Ionic channels (PolyP/PHB
i
complexes)

Degradosomes
Flagella
mRNA stability
Motility functions
regulation

Figure 7.9 The localization and functions of PolyPs in prokaryotes.

peripheral blood mononuclear cells and human blood plasma. The cellular content of PolyPs
in osteoblast-like cells significantly decreased after the combined treatment of cells with
stimulators of osteoblast proliferation and differentation (Leyhausen et al., 1998; Schr¨oder
et al., 1999, 2000). These authors assume that PolyPs may be involved in the modulation
of the mineralization process in bone tissue.
PolyP 3 was found to be a phosphodonor for the phosphorylation of some proteins in rat
liver microsomes (Tsutsui, 1986) and for nucleoside kinases, in particular human deoxyri-
bonucleoside kinases (Krawiec et al., 2003). This gives an additional possibility for the
involvement of PolyPs in the regulatory processes in animal cells.
Thus, in spite of the fact that animal cells, probably with the exception of bone tissue
cells, do not need PolyPs as phosphate reserves, the functions of these biopolymers are still