Page 89 - The Biochemistry of Inorganic Polyphosphates

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Enzymes of polyphosphate degradation 73
Itis probablethat a similar pathway of PolyP synthesis which isrelated to the biosynthesis
of some biopolymers may exist in bacteria. Undecaprenyl diphosphate, which could be
involved in this pathway, is found in bacteria.
6.2 Enzymes of Polyphosphate Degradation

6.2.1 Polyphosphate-Glucose Phosphotransferase
(EC 2.7.1.63)
This enzyme catalyses the phosphorylation of glucose using polyP or ATP as the phosphoryl
donor:
PolyP + D-glucose −−→ PolyP n−1 + D-glucose 6-phosphate (6.9)
n
The enzyme activity was first observed in Mycobacterium phlei (Szymona, 1957) and
then in numerous bacteria (Szymona et al., 1962; Szymona and Ostrowsky, 1964), in-
cluding other Mycobacteria (Szymona and Szymona, 1978), Corynebacterium diphtheriae
(Szymona and Szymona, 1961) and Nocardia minima (Szymona and Szymona, 1979).
The screening for polyphosphate glucokinase activities in a variety of different organisms
showed its presence in the phylogenetically ancient bacteria belonging to the Actinomyc-
etales (Szymona et al., 1967, 1969, 1977; Kulaev and Vagabov, 1983). This activity was
observed in Microlunatus phosphorus, a bacteria from activated sludge accumulating high
levels of PolyPs (Kuroda and Ohtake, 2000).
The enzyme activity was not found in eucaryotes. The discovery of this enzyme was of
the greatest significance for our understanding of the role of PolyPs: it provided the first
evidence of the possible function of PolyPs as a phosphate and energy donor without the
nucleoside phosphate system.
PolyP 3 and PolyP 4 were reported to be the end products formed from long-chain PolyPs
in glucose phosphorylation (Szymona and Widomski, 1974; Kowalczyk and Phillips, 1993).
PolyP glucokinase utilized polyP via a quasi-processive or non-processive mechanism
(Pepin and Wood, 1986, 1987; Hsieh et al., 1996a,b). The enzyme from Mycobacterium
tuberculosis utilizes a wide range of PolyP sizes by a non-processive mechanism (Hsieh
et al., 1996a). The enzyme from Propionibacterium shermanii, on the other hand, shows a
transition from a strictly processive mode with very long PolyPs to a strictly non-processive
mode with short PolyPs below 100 residues. Intermediate sizes of PolyPs (∼ 100–200
residues) are utilized by a quasi-processive mechanism, which is evidenced by a noticeable
broadening of the range of polyP sizes with the reaction time.
There have been numerous reports on the occurrence of various isoenzymes of polyphos-
phate glucokinase in different microorganisms and on differences in the molecular weights
of the enzyme in the same organism (Szymona et al., 1977; Kowalska et al., 1979;
Pastuszak and Szymona, 1980). Szymona et al. (1977) found that the molecular mass
of native enzyme from M. tuberculosis was 118 kDa, while Pastuszak and Szymona (1980)
found a larger form of the enzyme. The enzyme from M. phlei was found to be a protein
of 113 kDa (Szymona and Ostrowski, 1964) or 275–280 kDa (Girbal et al., 1989). The
native enzyme from P. shermanii was reported to have a molecular mass of 31 kDa (Clark,