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I have never seen anything comprehensively written about the vitamins necessary to metabolize amino acids through the citric acid cycle and gluconeogenesis pathway other than the following diagram written in Japanese. (I added the English translation) The source for this was created by a Japanese health food manufacturer(https://www.orthomolecular.jp/nutrition/vitamin_b/), so it's not completely reliable, but I'm looking for a well-organized diagram like this one.

enter image description here

The abbreviations for vitamins are as follows. However, the active forms of the vitamins are not distinguished, for example, TPP is vitamin B1, FAD is vitamin B2, NAD+ and NADPH are Niacin.

  • B1: Vitamin B1
  • B2: Vitamin B2
  • N: Niacin (vitamin B3)
  • P: Pantothenic acid (vitamin B5)
  • B6: Vitamin B6
  • Bio: Biotin (Vitamin B7)
  • F: Folic acid (Vitamin B9)
  • B12: Vitamin B12
  • C: Vitamin C

The above figure may be summarized as sentences as follows;

(1)Enter the citric acid cycle via pyruvate : Gly, Ala, Cys, Ser, Thr, Trp

(2)Enter the citric acid cycle via α-ketoglutarate : Gln, Arg, His, Pro,Glu

(3)Enter the citric acid cycle via succinyl-CoA: Met, Ile, Val

(4) Enters the citric acid cycle via fumaric acid :Phe, Tyr

(5) Directly to oxaloacetate: Asp, Asn

(6) Enters the citric acid cycle as acetyl-CoA (i.e., as a “ketogenic amino acid”)
Ketogenic only :leucine, lysine
Also glucogenic: isoleucine, tyrosine, phenylalanine, tryptophan, threonine

  • Tryptophan and lysine are converted to acetyl-CoA with the help of B2, P, N, and B6.
  • Of those exclusively ketogenic, it is not written about what vitamins are needed in the process of converting leucine to acetyl-CoA.
  • Of those that are also glucogenic, it is not written about what vitamins are required in the process of converting isoleucine, tyrosine, phenylalanine, and threonine to acetyl-CoA.

This is a long introduction, but what I want to accomplish in this thread are as follows;

My questions

  • What are the Vitamins required for the process of converting the Tryptophan into Pyruvate?
  • What vitamins are needed in the process of converting leucine to acetyl-CoA?
  • What vitamins are required in the process of converting isoleucine, tyrosine, phenylalanine, and threonine to acetyl-CoA?
  • If you notice, I would also like to know if there are any facts that are critically missing or apologized for in the above diagram or summary in terms of amino acid metabolism in the citric acid cycle.
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FYI: I could not find any articles written in English that was compact enough for my purposes. Therefore, I would like to share the content of a Japanese university's website with minimal annotations;http://www.sc.fukuoka-u.ac.jp/~bc1/Biochem/amino_met.htm

(1) Groups that enter the citric acid cycle via pyruvate: Gly, Ala, Cys, Ser, Thr, Trp

  • There is no mention of vitamins in the process of Ala → pyruvic acid.
  • ASP-(using NADPH2,NAD)→Thr→Gly-(using tetrahydrofolate)→Ser→pyruvic acid
  • Although not much has been written about Asp, it seems that it also enters the citric acid cycle via pyruvate.

enter image description here

(1)'Amino acids in this group other than alanine (Gly, Cys, Ser, Thr, and Trp) can also become succinyl-CoA.

  • All amino acids pass through threonine (except alanine)
  • Serine-(using THF) → Gly → Thr
  • ASP-(NADPH2, use NAD) → Thr
  • Thr is converted to succinyl-CoA with the assistance of NAD.
  • In the process of converting glycine to threonine, acetyl-CoA is produced as a secondary product.

(2) Group that enter the citric acid cycle via α-ketoglutarate: Gln, Arg, His, Pro, Glu

  • All amino acids pass through Glu
  • Gln becomes Glu without any special vitamin support
  • His becomes Glu with the assistance of THF
  • Pro becomes Glu with the assistance of FAD and NAD
  • Arg becomes Glu with the assistance of NAD
  • Finally, Glu becomes alpha-ketoglutarate (α-KG) with the help of NAD. enter image description here

(3) Groups that Enter the citric acid cycle via succinyl-CoA: Met, Ile, Val

  • Valine and leucine, with the aid of NAD and FAD, go through similar pathways to methylmalonyl CoA, which is then converted to succinyl CoA. enter image description here
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  • $\begingroup$ (+1) For "There is no mention of vitamins in the process of Ala → pyruvic acid." Vitamin B6 (pyridoxal phosphate), surely? $\endgroup$
    – user338907
    Dec 24, 2023 at 11:22

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