JTW's Evolutionary Origins - Author: Wood, John T.
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A Minimal Core for a Chemoautotrophic Metabolism

To account for coenzymes and the four major classes of biomolecules - lipids, sugars, amino acids, and nucleotides - the minimal core of a chemoautotrophic metabolism should comprise some form of the following biochemical pathways:

The Reductive Citric Acid Cycle (RCC)

(Krebs 1937, Evans, M. C. W., Buchanan, B. B. & Arron, D. I. 1966)

Glycolysis/Gluconeogenesis

(Embden-Meyerhof 1940)

The Amino Acid Pathways


The Pentose Phosphate Shunt

The Porphyrin Pathway

The Nucleotide Pathways

The Lipid Pathways

The RCC serves as the central metabolic hub. This is the junction where all pathways and their organic constituents, either directly or indirectly, emanate from (anabolic or synthesis metabolism) and converge to (catabolic or degradation metabolism). [There are exceptions, i.e. CO2, Urea, Carbomyl-Phosphate]. The RCC has the following points of intersection with the rest of the metabolic network.
  • The Alpha-Keto Acids - Pyruvate, Alpha-Ketoglutarate, and Oxaloacetate

    • Pyruvate --> Ala, Leu, Val
    • Oxaloacetate --> Asp, Asn, Ile, Lys, Thr, Arg, Orn, RNA/DNA
    • Alpha-Ketoglutarate --> Glu, Gln, Arg, Pro

    • Glycolysis, Ala, Cys, Gly, Ser, Thr, Trp --> Pyruvate
    • Asn, Asp --> Oxaloacetate
    • Arg, His, Pro, Gln, Glu --> Alpha-Ketoglutarate

  • Fumarate

    • Phe, Tyr, Asp --> Fumarate

  • Succinyl-Coenzyme A (Succinyl-CoA)

    • Succinyl-CoA --> Porphyrins

    • Odd # Fatty Acids --> Succinyl-CoA

  • Acetyl-Coenzyme A (Acetyl-CoA)

    • Acetyl-CoA --> Lipids
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