Page 81 - The Biochemistry of Inorganic Polyphosphates

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ENZYMES OF

POLYPHOSPHATE

BIOSYNTHESIS AND

DEGRADATION

6.1 Enzymes of Polyphosphate Biosynthesis

6.1.1 Polyphosphate Kinase (Polyphosphate:ADP
Phosphotransferase, EC 2.7.4.1)

The reaction of reverse transfer of energy-rich phosphate residues from ATP to PolyPs
and from PolyPs to ADP, thus linking energy-rich pools, was discovered by Kornberg and
co-workers (Kornberg et al., 1956; Kornberg, 1957 a,b):

PolyP + ATP PolyP n + 1 + ADP (6.1)
n
The enzyme was partly purified from Propionibacterium shermanii (Robinson et al.,
1987), and was shown to be a monomeric enzyme with a molecular mass of ∼ 83 kDa. It
was demonstrated that short-chain PolyPs of 6–80 residues serve as primers for the synthesis
of long-chain PolyPs using ATP by a strictly processive mechanism. The largest PolyPs
synthesized was PolyP 750 .
The polyphosphate kinase (ppk1) purified from Escherichia coli was a membrane-bound
homotetramerwithasub-unitmolecularmassof80kDa(AhnandKornberg,1990;Akiyama
et al., 1992). The crystal structure of this enzyme has been determined (Zhu et al., 2003).
This enzyme is responsible for the processive synthesis of long PolyP 750 chains in vivo
and needs Mg 2+ for its activity (Ahn and Kornberg, 1990). The enzyme was shown to be
multifunctional. It catalyses the reverse reaction of ATP synthesis from PolyPs (Kornberg,
1957a; Murata et al., 1988; Ahn and Kornberg, 1990; Kuroda and Kornberg, 1997) and

The Biochemistry of Inorganic Polyphosphates I. S. Kulaev, V. M. Vagabov and T. V. Kulakovskaya
C 2004 John Wiley & Sons, Ltd ISBN: 0-470-85810-9

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