Page 163 - The Biochemistry of Inorganic Polyphosphates

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Yeast 147
It should be noted that no ppx or ppk similar genes were found in Halobacterium genome
(Cardona et al., 2002). There are little data on exopolyphosphatase activity in other Archae.
In Sulfolobus solfactaricus (Cardona et al., 2002) this was very low – much less than in
bacteria. In Sulfolobus solfactaricus, however, a functionally active gene of exopolyphos-
phatase was found (Cardona et al., 2002) with a similarity to bacterial ppx. In other archaeal
genomes, putative genes similar to the yeast PPX1 or bacterial ppx genes have been revealed
(Cardona et al., 2002). However, the functional activity and significance of the proteins en-
coding by these genes are still unclear.

8.10 Yeast

Yeasts are the microorganisms where PolyPs were first discovered (Liebermann, 1888).
Many papers and reviews summarize the available data on PolyP metabolism and functions
in these organisms (Schmidt et al., 1946; Hoffman-Ostenhof and Weigert, 1952; Wiame,
1947a,b, 1948, 1949; Hoffmann-Ostenhof et al., 1955; Yoschida, 1955a,b; Langen and Liss,
1958a,b, 1959; Kulaev and Belozersky, 1962a,b; Harold, 1966; Weimberg and Orton, 1964,
1965; Weimberg, 1970; Dawes and Senior, 1973; Matile, 1978; Kulaev, 1971, 1974; Kulaev
and Vagabov, 1983; Kornberg, 1995, Kornberg et al.,1999; Kulaev et al., 1999; Kulaev and
Kulakovskaya, 2000), and here we will cite only some of these.
The content of PolyPs in yeast cells strongly depends on the culture conditions and
growth stage and can be as much as 10 % of the total dry weight of a yeast cell (Salhany
et al., 1975). In P i complete media, the highest values of PolyPs were observed in the
stationary phase. PolyPs with chain lengths of as low as 3–8 to as high as 200–260 were
obtained from the cells of these microorganisms by chemical extraction (Langen and Liss,
1959; Schuddemat et al., 1989a).
It should be noted that yeast possesses PolyPs in nearly all cell compartments (see Chap-
ter 5) and the compartmentation of these biopolymers should be taken into consideration
when analysing their accumulation and utilization.

8.10.1 Yeast Cells Possess Different
Polyphosphate Fractions

The content of PolyP in yeast cells was determined by various techniques, including chem-
31
ical extraction, P NMR spectroscopy, enzymatic, and electrophoretic methods (see Chap-
ter 2). One of the most suitable methods for the study of PolyPs in yeasts is chemical
extraction (Langen and Liss, 1958a,b; Chernyscheva et al., 1971; Vagabov et al., 1998),
which made it possible to isolate five PolyP fractions.
The acid-soluble fraction, PolyP(I), was extracted with 0.5 M HClO 4 (or 10 % tri-
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choroacetic acid) at 0 C for 30 min. The salt-soluble fraction, PolyP(II), was extracted
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with a saturated solution of NaClO 4 at 0 C for 1 h. The weak alkali-soluble fraction,
PolyP(III), was extracted with weak NaOH, pH 9–10, at 0 C for 30 min. The alkali-soluble
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fraction, PolyP(IV), was extracted with 0.05 M NaOH at 0 C for 30 min. The last fraction,
PolyP(V), was assayed by the amount of P i which appeared after the hydrolysis of biomass
in 0.5 M HClO 4 at 90 C for 40 min.
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