Page 211 - The Biochemistry of Inorganic Polyphosphates

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Phosphorus compounds in chemical evolution 195
compound and the hydrolysis of its phosphoric anhydride bond liberated 4.5–5 kCal of
energy per mole (Flodgaad and Fleron, 1974).
In model experiments, the conditions were found for non-enzymatic synthesis of py-
rophosphate, by the phosphorylation of orthophosphate in the presence of certain cations,
and by means of ATP and PolyP 3 , respectively (Lowenstein, 1958; Tetas and Lowenstein,
1963; Le Port et al., 1971).
It was shown experimentally that this reaction proceeded much more rapidly with PolyP,
as follows (Kulaev and Skryabin, 1971, 1974):
32 32
PolyP n + [ P] orthophosphate −−→ [ P] pyrophosphate + PolyP n−1 (10.1)
It was observed that radioactive pyrophosphate was formed non-enzymatically in sub-
32
stantial amounts when [ P] orthophosphate was phosphorylated by incubation with PolyP 40
in an aqueous solution at 37 C for 15 h at pH 9 in the presence of certain divalent cations.
◦
The 16–30 % of initial high-molecular-weight polyphosphate was utilized in phosphoryla-
tion, and among the cations tested, the greatest amount of incorporation was achieved with
Ba 2+ (33 %) and the least with Mg 2+ (16 %):
Cation Mg 2+ Ca 2+ Mn 2+ Cd 2+ Ba 2+ None

PP i / PolyP (× 100 %) 16 22 23 26 33 0

It is interesting that, when organic and inorganic tripolyphosphates were employed under
the same conditions, only 0.2–0.6 % of the phosphate donor was utilized (Lowenstein,
1958, 1960; Tetas and Lowenstein, 1963; Le Port et al., 1971). Our experimental findings
thus lead to the conclusion that, as the Earth cooled and a hydrosphere was formed on
its surface, a variety of transphosphorylation reactions became possible in the primeval
ocean, in particular, the phosphorylation of P i by PolyP to give pyrophosphate. It should
be noted that the non-enzymatic synthesis of PolyP and pyrophosphate on the primitive
Earth could take place not only in solutions, but also on the surface of some minerals with
anion-exchange properties (Arrhenius et al., 1993, 1997).

10.2 Phosphorus Compounds in Chemical Evolution

Phosphate ion is a unique link between living organisms and the inorganic world. In the
opinion of some investigators (Arrhenius et al., 1993; De Graaf et al., 1998; Arrhenius et al.,
1997), among anionic species oligophosphate ions and charged phosphate esters could have
been of great importance in the proposed ‘RNA world’. Phosphorylation is shown to result
in selective concentration by surface sorption of compounds, otherwise too dilute to support
condensation reactions. It provides protection against rapid hydrolysis of sugars and induces
oligomerization of aldehydes by selective concentration. As a manifestation of life arisen,
phosphate already appears in the organic context in the oldest preserved sedimentary record
(Arrhenius et al., 1997).
Some experiments have shown efficient condensation of simple aldehyde phosphates
in the hydroxide mineral (such as hydrotalcite, ([Mg 2 Al(OH) 6 ][nH 2 O]) interlayer to form