Figure 6.

Summary of the final conversion of dietary protein amino acids in 1C, 2C, 3C, 4C, and 5C fragments, which revert essentially into 3C and 2C, during the human catabolism of amino acid hydrocarbon-skeletons. The pathways used to prepare this graph are the most common, including the main alternate pathways [105]. The green lines show the carbon paths for each amino acid, the brown lines represent the relationship between the core of the TCA cycle and pyruvate dehydrogenase (with the loss of one CO₂ between each substrate group box (marked in yellow). Non-standard abbreviations: Hyp = L-4-hydroxyproline; Orn = ornithine; “1C” = One-carbon fragment donor systems.