Page 114 - The Biochemistry of Inorganic Polyphosphates

WU095/Kulaev
WU095-07
Functions of polyphosphate and polyphosphate-dependent enzymes
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Table 7.1 The concentrations of K ,Mg 2+ and P i in
+
cytosol and vacuoles of Saccharomyces carlsbergensis
(Okorokov et al., 1980; Lichko et al., 1982).
Concentration (mM)
Ion Cytosol Vacuoles
K + 60 470
Mg 2+ 5 73
1 110
P i

Table 7.2 The accumulation of Mn 2+ (µmol per g of wet biomass), P i (µmol per g of wet
biomass) and PolyP (µmol of P per g of wet biomass) in the cells of S. carlsbergensis. The
cells were pre-incubated with KH 2 PO 4 and glucose (Lichko et al., 1982).
Cells after 60 min
Cells before incubation incubation with
Compartment Compound with Mn 2+ Mn 2+ and glucose
Cytoplasm P i 1.9 1.3
PolyP 3.7 3.9
Osmotically free Mn 2+ < 0.1 1.2
Vacuole P i 34.0 27.4
PolyP 25.5 38.4
Osmotically free Mn 2+ < 0.1 2.8
Bound Mn 2+ < 0.1 9.5

Arginine accumulated in vacuoles was shown to form a complex with PolyP (D¨urr et al.,
1979; Cramer and Davis, 1984). In the vacuoles of Neurospora crassa, spermidine was
found along with arginine, and almost half of the PolyP in these organelles was considered
to form complexes with these positively charged compounds (Cramer and Davis, 1984), in
spite of the existence of an independent regulation of vacuolar pools of basic compounds
and PolyP under some culture conditions (Cramer et al., 1980).
The accumulation of Mn 2+ in the vacuoles of Saccharomyces carlbergensis (Lichko
et al., 1982) correlated well with the increase in PolyP content (Table 7.2). During the
accumulation of Mn 2+ by S. carlsbergensis, both of the PolyP and Mn 2+ contents increased
simultaneously. This accumulation took place even when the incubation medium contained
no P i and was accompanied by a simultaneous decrease of P i content in the vacuoles. This
complex-forming function of PolyP may be very important for the yeast cell, since under a
short-term phosphate starvation in the presence of metal cations in the medium the vacuolar
PolyP content slightly decreases (Table 7.3) (Lichko et al., 1982). A stable P i content in the
cytosol under the above conditions is maintained mainly due to a decrease in the vacuolar P i
pool but not in the vacuolar PolyP pool. It is probable that the ability of fungi to accumulate
large amounts of heavy metals is connected with the PolyP pools, especially in vacuoles.