Citric acid cycle evolution

Rotte C, Stejskal F, Zhu G, Keithly JS, Martin W (2001) Pyruvate NADP+ oxidoreductase from the mitochondrion of Euglena gracilis and from the apicomplexan Cryptosporidium parvum a biochemical relic linking pyruvate metabolism in mitochondriate and amitochondriate protists. Mol Biol Evol 18 710-720 Schnarrenberger C, Martin W (2002) Evolution of the enzymes of the citric acid cycle and the glyoxylate cycle of higher plants. A case study of endosymbiotic gene transfer. Eur J Biochem 269 868-883... 

A multiauthor book on the citric acid cycle, including molecular genetics, regulatory mechanisms, variations on the cycle in microorganisms from unusual ecological niches, and evolution of the pathway. Especially relevant are the chapters by H. Gest (Evolutionary Roots of the Citric Acid Cycle in Prokaryotes),... 

Gest, H., Evolutionary roots of the citric acid cycle in prokaryotes. Biochem. Soc. Symp. 54 3-16, 1987. A fascinating recount of how the evolution of the cycle is traced by studying the way in which enzymes of the cycle are used in present day microorganisms. 

According to a general rule of organic chemistry, reactions involving the smallest molecules are catalytically the most restrictive. This rule holds notably for the build-up of carbon skeletons with the arithmetic Cl -F Cl = C2 (e.g., C2 = glycine or acetyl thioester). Therefore, it may not come as a surprise that in the course of metabolic evolution, these most simple carbon fixation reactions may fall by the wayside. Under these conditions, an autotrophic carbon fixation metabolism can only be maintained by a metabolic cycle, which multiplies the C2 unit autocatalytically in the absence of its de novo synthesis. A prominent example is the reductive citric acid cycle (C2 -F Cl... 

Evolution of succinyl CoA synthetase Section 17.1.7 Evolutionary history of the citric acid cycle Section 17,3,3 Endosymbiotic origins of mitochondria Section 18.1.2... 

How did the citric acid cycle come into being Although definitive answers are elusive, it is nevertheless instructive to speculate how this complicated central hub of metabolism developed. We can perhaps begin to comprehend how evolution might work at the level of biochemical pathways. 

E. Melendez-Hevia, T.G. Waddell, and M. Cascante. 1996. The puzzle of the Krebs citric acid cycle Assembling the pieces of chemically feasible reactions, and opportunism in the design of metabolic pathways in evolution J. Mol. Evol. 43 293-303. (PubMed)... 

The purification of the IRE-BP and the cloning of its cDNA were sources of truly remarkable insight into evolution. The IRE-BP was found to be approximately 30% identical in amino acid sequence with the citric acid cycle enzyme aconitase from mitochondria. Further analysis revealed that the IRE-BP is, in fact, an active aconitase enzyme it is a cytosolic aconitase that had been known for a long time, but its function was not well understood (Figure... 

Huynen, M. A., Dandekar, T., and Bork, P., Variation and Evolution of the Citric Acid Cycle A Genomic Perspective, Trends Microbiol., 7 281-291, 1999. 

Some anaerobic organisms have developed only parts of the citric acid cycle, which they use exclusively to make the important precursors. These simple yet important reactions emphasize the truly connected nature of what we often artificially separate into pathways. They also illustrate the convergence of evolution to a few key molecules and metabolic steps. 

Since conserved strnctures with a very long lifetime have a great advantage in the evolution, a biological system is used over and over again. The result is cyclic reactions where reactants are fed in along a pathway and products are given away. There are several examples in Natnre, for example, the citric acid cycle and the Calvin cycle. 

The citric acid cycle has been found to take place in microorganisms and plant seedlings as well as in the cells of animals. The existence of this common feature, as well as others, indicates a common origin, as is assumed in the theory of evolution. There is evidence that for some microorganisms the cycle serves mainly to produce molecules with special structure for special purposes (such as a-ketoglutaric acid for the synthesis of glutamic acid and some other amino acids). For man and other animals it supplies both these special substances and energy. 

Cooper et al [285] and Saladino et al. [286] identified pyravic, oxaloacetic, citric, isocitiic and a-ketoglutaric acids (all members of the citric acid cycle) in carbonaceous meteorites and as products of pyravic acid reactions at low temperatures. Oxaloacetic and pyruvic acids in series of reactions can be converted to citric acid [287, 288], Considering that meteorites deliver a variety of organic compounds to Earth, most likely, their role in the origin of life and in the evolution of biochemical pathways can not also be excluded. 

Waddell TG, Geevarghese SK, Henderson BS, Pagni RM, Newton JS (1989) Chemical evolution of the citric acid cycle sunlight and ultraviolet photolysis of cycle intermediates. Grig Life Evol Biosph 19 603 07... 

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