Page 161 - The Biochemistry of Inorganic Polyphosphates

20:32
Char Count= 0
March 9, 2004
WU095/Kulaev
WU095-08
Archae 145
effect on polyphosphate kinase activity and only a slight, but nevertheless definite, effect
on 1,3-diphosphoglycerate–polyphosphate phosphotransferase activity. The polyphosphate
glucokinase activity remained at a high level during the whole time of cultivation and was
not affected by polymyxin. Polymyxin M, when added to the growth medium, significantly
increases (by a factor of 2–7) the activity of exopolyphosphatase and tripolyphosphatase.
This is an indication that the functioning of these enzymes may be closely bound (as
in other microorganisms) with the cytoplasmic membrane, which is the site of action of
polymyxin M. The polyphosphatase evidently plays an important part in PolyP degrada-
tion. As soon as this enzyme activity begins to appear, PolyP accumulation ceases. In the
presence of polymyxin, the increase of this activity correlated with the reduction in the
PolyP level.
Great contributions to the studies of PolyP metabolism were made by Wood and co-
workers (Clark et al., 1986; Clark and Wood 1987; Wood and Clark, 1988). These work-
ers obtained three PolyP fractions from P. shermanii, i.e. short-chain PolyPs soluble in
trichloroacitic acid, long-chain PolyPs soluble at neutral pH, and long-chain PolyPs present
in volutin granules. Cells grown on lactate did not contain short-chain PolyPs but did con-
tain a high amount of long-chain PolyPs, which accumulated to 3 % of the dry cell biomass
(Clark et al., 1986). At least 70 % of this PolyP was present in volutin granules. The PolyPs
ranged from 250 to 725 phosphate residues and were of the same average size as those
synthesized in vitro by polyphosphate kinase from this bacterium. In contrast to the cells
grown on lactate, the glucose-grown cells did not contain volutin granules, but did contain
short-chain PolyPs with an average chain length of 25–75 residues. It has been proposed that
the amounts and chain lengths of the PolyPs are lower during growth on glucose, because
they are utilized as substrates in the phosphorylation of glucose by polyphosphate glucok-
inase present in this organism (Wood and Clark, 1988). Later, polyphosphate glucokinase
from this organism was purified, cloned and characterized (for reference, see Chapter 6).
Data indicating participation of PolyPs in overcoming stress were obtained in Propi-
onibacteria. The PolyP component in the 31 P NMR spectra of Propionibacterium acne
increased after ultraviolet light irrardiation (Kjeldstad and Johnson, 1987) and after hyper-
thermia treatment (Kjeldstad et al., 1988). Such treatments, carried out in triplicate, induced
31
an increase in the PolyP content, as observed by P NMR spectroscopy. One of the expla-
nations for this might be that hyperthermia and ultraviolet light induce an oxidative stress
in the cells, which increases the amount of PolyP (Kjeldstad and Johnson, 1987; Kjeldstad
et al., 1988).
To summarise, it should be said that the PolyP content and chain length in Propionibac-
teria are strongly dependent on the carbon source. These bacteria possess polyphosphate
glucokinase and are able to directly utilize PolyP for glucose phosphorylation.

8.9 Archae

PolyP metabolism in Archae, a very ancient and heterogenic domain of prokaryotes, has
been little studied. PolyP and PolyP-dependent enzymes were observed in some represen-
tatives of this domain (Scherer and Bochem, 1983; Skorko, 1989; Trotsenko and Shishkina,
1990; Rudnick et al., 1990; Andreeva et al., 2000; Smirnov et al., 2002a,b; Cardona et al.,
2002).