A reverse KREBS cycle in photosynthesis: consensus at last

@article{Buchanan2004ARK,
  title={A reverse KREBS cycle in photosynthesis: consensus at last},
  author={Bob B. Buchanan and Daniel I. Arnon},
  journal={Photosynthesis Research},
  year={2004},
  volume={24},
  pages={47-53}
}
The Krebs cycle (citric acid or tricarboxylic acid cycle), the final common pathway in aerobic metabolism for the oxidation of carbohydrates, fatty acids and amino acids, is known to be irreversible. It liberates CO2 and generates NADH whose aerobic oxidation yields ATP but it does not operate in reverse as a biosynthetic pathway for CO2 assimilation. In 1966, our laboratory described a cyclic pathway for CO2 assimilation (Evans, Buchanan and Arnon 1966) that was unusual in two respects: (i) it… 
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References

SHOWING 1-10 OF 75 REFERENCES
Role of the reductive carboxylic acid cycle in a photosynthetic bacterium lacking ribulose I,5-diphosphate carboxylase.
TLDR
The results show that CO 2 concentration influences the products formed by the reductive carboxylic acid cycle, with a low level of CO 2 favoring the synthesis of carbohydrates.
Autotrophic CO2 fixation in Chlorobium limicola. Evidence against the operation of the Calvin cycle in growing cells
TLDR
Chlorobium limicola has been proposed to assimilate CO2 autotrophically via a reductive tricarboxylic acid cycle rather than via the Calvin cycle, and studies of the cell components support this interpretation.
Carbon Isotope Fractionation by Autotrophic Bacteria with Three Different C02 Fixation Pathways
Abstract Carbon isotope fractionation during autotrophic growth o f different bacteria which possess different autotrophic CO2 fixation pathways has been studied. 13C /12C -Ratios in the cell carbon
Carbon assimilation pathways in sulfate-reducing bacteria II. Enzymes of a reductive citric acid cycle in the autotrophic Desulfobacter hydrogenophilus
TLDR
The data indicate that in D. hydrogenophilus a reductive citric acid cycle is operating in autotrophic CO2 fixation, and since other autotrophic sulfate reducers possess an acetyl CoA pathway for CO2fixing, two different autOTrophic pathways occur in the same physiological group.
Citric-acid cycle, 50 years on
TLDR
A second pathway for acetyl-CoA oxidation was found and it is shown that sulfur-reducing bacteria and one genus of sulfate reducers use a modified citric-acid cycle with a novel anaplerotic sequence as pathway of terminal respiration, while all other anaerobes use an alternative pathway.
Autotrophic CO2 fixation in Chlorobium limicola. Evidence for the operation of a reductive tricarboxylic acid cycle in growing cells
TLDR
All reactions of the proposed reductive tricarboxylic acid cycle could be demonstrated in autotrophically growing cells.
Further studies on carbon dioxide fixation in Chlorobium
  • R. Sirevåg
  • Biology, Medicine
    Archives of Microbiology
  • 2004
TLDR
The pathway of carbon in photosynthesis of Chlorobium thiosulfatophilum strain 8346 was examined and Succinic acid showed a high specific activity after exposure of the cells to 14CO2, indicating that this compound might be formed by a direct carboxylation reaction as well as by the reactions of the reductive tricarboxylic acid cycle.
Role of ferredoxin in the synthesis of alpha-ketobutyrate from propionyl coenzyme A and carbon dioxide by enzymes from photosynthetic and nonphotosynthetic bacteria.
  • B. Buchanan
  • Biology, Medicine
    The Journal of biological chemistry
  • 1969
TLDR
Evidence is presented for a new carboxylation reaction, designated the α-ketobutyrate synthase reaction, which involves a ferredoxin-dependent reductive carboxyation of propionyl coenzyme A to α- ketobutirate, which provides a new mechanism for the reductive assimilation of propionsate and CO2.
Enzymes of the Reductive Pentose Phosphate Cycle
Thirteen enzyme-catalyzed reactions constitute the Calvin cycle of CO2 fixation (Fig. 1). Evidence for all these reactions was obtained in the 1950’s, and in the last two decades each reaction has
Carbon dioxide fixation in green sulphur bacteria.
TLDR
It is concluded that in washed suspensions, CO(2) is fixed mainly by a mechanism involving the reductive carboxylic acid cycle, and appears to exhibit a similar pattern to that in C. thiosulfatophilum strain 8346.
...
1
2
3
4
5
...