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The viability of a nonenzymatic reductive citric acid cycle - Kinetics and thermochemistry

Origins of Life and Evolution of the Biosphere

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DOI: 10.1007/s11084-006-9017-6

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Abstract

The likelihood of a functioning nonenzymatic reductive citric acid cycle, recently proposed as the precursor to biosynthesis on early Earth, is examined on the basis of the kinetics and thermochemistry of the acetate ??? pyruvate ??? oxaloacetate ??? malate sequence. Using data derived from studies of the Pd-catalyzed phosphinate reduction of carbonyl functions it is shown that the rate of conversion of pyruvate to malate with that system would have been much too slow to have played a role in the early chemistry of life, while naturally occurring reduction systems such as the fayalite-magnetite-quartz and pyrrhotite-pyrite-magnetite mineral assemblages would have provided even slower conversions. It is also shown that the production of pyruvate from acetate is too highly endoergic to be driven by a naturally occurring energy source such as pyrophosphate. It is thus highly doubtful that the cycle can operate at suitable rates without enzymes, and most unlikely that it could have participated in the chemistry leading to life. ?? 2006 Springer Science + Business Media B.V.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The viability of a nonenzymatic reductive citric acid cycle - Kinetics and thermochemistry
Series title:
Origins of Life and Evolution of the Biosphere
DOI:
10.1007/s11084-006-9017-6
Volume
37
Issue:
1
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Origins of Life and Evolution of the Biosphere
First page:
61
Last page:
65