Page 195 - The Biochemistry of Inorganic Polyphosphates

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Animals 179
Table 8.11 Occurrences of PolyPs in animals
(Kumble and Kornberg, 1995; Kornberg, 1999).
System PolyP (µM)
Rat liver 26
Cytosol 12
Nucleus 89
Rat brain 54
Rat heart 58
Rat kidneys 34
Rat lungs 26
Mouse brain 95
Mouse heart 114

addition, exopolyphosphatase and endopolyphosphatase were found in animal cells
(Kumble and Kornberg, 1996; Schr¨oder et al., 1999, 2000).
It is rather difficult to compare the earlier and more recent data on the PolyP contents in
animal tissues, because these have been calculated in different ways. However, animal tis-
sues contain less PolyPs than microorganisms. Thus, here we present the data from the work
of Kornberg and co-workers in Table 8.11 (Kumble and Kornberg, 1995; Kornberg, 1999)
and from the work of Schr¨oder and co-workers in Table 8.12 (Schr¨oder et al., 1999, 2000).
The latter table shows the concentrations measured for ‘soluble’ long-chain PolyPs (mainly
polymers of 10–50 P i residues) and ‘insoluble’ long-chain PolyPs (mainly polymers of >
50 P i residues) in different cells and extracellular fluids from animals. The concentrations
of soluble long-chain PolyPs were determined to be higher than those of insoluble long-
chain PolyPs. PolyPs was also present extracellularly in human blood plasma and serum.
However, the concentrations of insoluble long-chain PolyPs in cell-free blood fractions is
much lower those in human peripheral blood mononuclear cells (PBMCs) and erythrocytes.
It is not yet known whether the plasma PolyPs are synthesized within this body fluid or
appear as a result of the lysis of erythrocytes, as suggested by its smaller size. The highest
amounts of PolyPs in humans were found in bone-forming osteoblasts (see Table 8.12).
Some interesting data on the changes in PolyP content and chain length were obtained
during the development of lower (sponge) and higher (mammals) animals.
Dramatic changes in PolyP metabolism were revealed in the course of gemmule germi-
nation in the freshwater sponge Ephydatia muelleri (Imsiecke et al., 1996). In the process of
germination, a rapid rise in the exopolyphosphatase activity and a strong decrease (by 94 %
in 2 d) in the PolyP level were observed (Imsiecke et al., 1996). Since germination does not
require exogenic energy sources, it was proposed that PolyP can serve as a phosphate and
energy source for this process (Imsiecke et al., 1996; Schr¨oder et al., 1999).
The interrelation of PolyP and RNA synthesis was observed in the course of embryonal
development of the frog (Shiokawa and Yamana, 1965) and at early stages of rat liver
regeneration (Mansurova et al., 1975a).
The PolyP content and exopolyphosphatase activity in rat tissues changed in the course of
ageing and development (Lorenz et al., 1997a). The PolyP level in rat brain increased sixfold