Page 214 - The Biochemistry of Inorganic Polyphosphates

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Polyphosphates in chemical and biological evolution
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complexes might be present in the coacervates and provide an exchange of micro- and
macromolecules between these proto-cells. The investigations of Reusch (Reusch, 1999a;
2000) showed that these channels exist in the membranes of nearly all classes of organisms
and probably were ancient membrane channels. Earlier, Gabel (1965, 1971) proposed the
involvement of PolyPs in formation of the first cell membranes.

10.3 Polyphosphates and Pyrophosphates: Fossil
Biochemical Reactions and the Course of
Bioenergetic Evolution

Model experiments, however, have not yet provided any reliable information concerning
the functions of high-molecular-weight PolyPs and pyrophosphate in the earliest living
creatures, although some conclusions as to the role of these primitive high-energy com-
pounds in the metabolism of protobionis may be drawn from comparative biochemistry. By
studying the metabolism of more ancient, comparatively primitive forms of contemporary
organisms, there may be discerned, as Lipmann (1971) has said, ‘antediluvian’ metabolic
features and fossil biochemical reactions, which have been preserved since ancient times.
Investigations in this field of biochemistry, which could be termed as ‘biochemical
palaeontology’, could lead, and have indeed led, to the detection of archaic metabolic
features, which in all probability derive from primitive life forms.
Thus, Baltscheffsky and co-workers (Baltscheffsky, 1967a,b; Baltscheffsky et al., 1966)
and Keister et al. (Keister and Yike, 1967a,b; Keister and Minton, 1971, 1972) have shown
that in the phylogenetically ancient and primitive photosynthesizing bacterium Rhodospir-
illum rubrum photosynthetic phosphorylation results in the production of high-energy phos-
phate much more in the form of pyrophosphate than in the form of ATP. The synthesis of
pyrophosphate can proceed in the chromatophores of this bacterium even when the forma-
tion of ATP is totally suppressed. Later, it was shown that pyrophosphate in Rhodospirillum
rubrum is accumulated only in light (Keister and Minton, 1971, 1972; Kulaev et al., 1974a).
The energy stored in the pyrophosphate molecule could be utilized both for reversed elec-
tron transport and for the active transport of ions through the chromatophore membranes in
this bacterium (Baltscheffsky, 1967a,b; Baltscheffsky et al., 1966).
The light-dependent synthesis of pyrophosphate was also observed in the chloroplasts
of higher plants (Rubtsov et al., 1977). The results obtained by Libermann and Skulachev
(1970) supposed that the energy of pyrophosphate in chromatophores of Rhodospirillum
+
rubrum is utilized via electrochemical proton potential ( µH ). The gene of proton-
pumping PP i synthetase from Rhodospirillum rubrum was cloned (Baltscheffsky et al.,
1998) and appeared to have a homology with plant vacuolar H PPases (Baltscheffsky
+
et al., 1999). In the vacuolar membranes of plants (Davies et al., 1997) and yeast (Lichko
+
+
and Okorokov, 1991), H PPases generate µH by using the energy of the PP i phospho-
anhydride bond. The vacuolar membranes of some archae and protozoa also possess such
H PPase (Drozdowicz et al., 1999; Docampo and Moreno, 2001).
+
Mansurova and co-workers (Mansurova et al., 1973a,b, 1975b, 1976; Mansurova, 1989)
have shown that the same process occurs in animal and yeast mitochondria. Pyrophosphate
is synthesized in rat liver mitochondria together with ATP (Figure 10.2). However, in rat liver