Page 75 - The Biochemistry of Inorganic Polyphosphates

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Eukaryotes 59
Table 5.2 Contents of PolyPs and other phosphorus compounds in the cells, protoplasts,
and nuclei of Neurospora crassa (expressed as mg of P per g of dry mycelium) (Kulaev
et al., 1966a; Krasheninnikov et al., 1967, 1968).
Phosphorus compound Whole cells Protoplasts Nuclei
Total PolyP 5.6 3.0 0.2
Acid-soluble PolyP(I) 1.8 1.8 0.0
Salt-soluble PolyP(II) 1.0 1.2 0.2
Alkali-soluble PolyP(IV) 2.0 0.0 0.0
Hot-HClO 4 -extractible PolyP(V) 0.8 0.0 0.0
Orthophosphate (P i ) 1.1 3.0 0.0
P i plus total PolyP 6.7 6.0 0.2
Nucleotides 1.2 1.0 0.1
Nucleic acids 6.7 6.9 0.6
Phospholipids 2.1 2.1 0.4
Sugar phosphates 0.4 0.5 0.2

Total phosphorus 17.3 17.2 1.5

amount of different PolyP fractions differed considerably in N. crassa (Table 5.2). When the
protoplasts were produced, the PolyPs of alkali and hot perchloric acid extracts disappeared
completely, while the acid-soluble and salt-soluble fractions remain unchanged. The disap-
pearance of some parts of the PolyPs was accompanied by a corresponding increase in the
amount of P i . This leads to the conclusion that the cell wall removal results in hydrolysis of
the above-mentioned highly polymerized PolyP to P i . It is possible that these PolyP fractions
are in some way bound to the cytoplasmic membrane of N. crassa and the formation of pro-
toplasts stimulates their hydrolysis. It is probable that these fractions are far more sensitive
to the integrity of cell structure than the acid-soluble and salt-soluble fractions. If the cells
of N. crassa were incubated with the snail enzyme for a longer time, substantial amounts
of P i and acid-soluble PolyPs were also lost. The salt-soluble fraction remained in the same
amount as in the whole cells. The different behaviour of the PolyP fraction during protoplast
formation from the cells of N. crassa indicated their different localization. It is likely that
the fractions isolated by the ‘Langen and Liss method’ (Langen and Liss, 1958a,b) from
N. crassa cells differ from each other not only in their molecular mass, but also in their in-
tracellular localization and state in the cell. Thus, the most highly polymerized fractions are
apparently located at the periphery of the cells, and removal of the cell walls results in their
rapid hydrolysis. The less polymerized, acid-soluble PolyPs are evidently located within
the cell, probably in the free state. In contrast to these fractions, the salt-soluble PolyPs
in N. crassa are located in such a way that the protoplast formation has no effect on their
amounts.
The removal of 30–35 % PolyPs from yeast cells during the lysis of cell walls by the
snail enzyme was observed in Saccharomyces carlbergensis (Vagabov et al., 1973) – these
were alkali-soluble fractions (Table 5.3). A comparative investigation of the amounts of
various PolyP fractions was carried out in E. magnusii spheroplasts (Table 5.4.) and some
sub-cellular fractions (Table 5.5). All of these data confirm the idea of PolyP localization
in different compartments of cells of the lower eukaryotes.