Pathway · 2 proteins
Folate-linked carbon transfer
One-carbon units support multiple biosynthetic reactions.
How it works
- The glycine cleavage system is annotated in full: GcvPA and GcvPB form the aminomethyl-transferring dehydrogenase, GcvT is the aminomethyltransferase, and GcvH is the lipoate-bearing carrier that hands the methylamine between them.
- The reaction releases CO2 and ammonia and transfers a methylene unit to tetrahydrofolate, so glycine cleavage is simultaneously a catabolic step and a one-carbon source.
- FolD and methylenetetrahydrofolate reductase then distribute those units between biosynthesis and methyl transfer. This is why the module sits inside central carbon: it is the junction between carbon skeletons and folate chemistry.
Grouped by the atlas’s curated pathway map. The table order is not a proven reaction order.
Its proteins
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| Probable glycine dehydrogenase (decarboxylating) subunit 1 | 1.4.4.2 | N(6)-[(R)-lipoyl]-L-lysyl-[glycine-cleavage complex H protein] + glycine + H(+) = N(6)-[(R)-S(8)-aminomethyldihydrolipoyl]-L-lysyl-[glycine-cleavage complex H protein] + CO2 | — | 439 | Step named |
| Aminomethyltransferase | 2.1.2.10 | N(6)-[(R)-S(8)-aminomethyldihydrolipoyl]-L-lysyl-[protein] + (6S)-5,6,7,8-tetrahydrofolate = N(6)-[(R)-dihydrolipoyl]-L-lysyl-[protein] + (6R)-5,10-methylene-5,6,7,8-tetrahydrofolate + NH4(+) | — | 350 | Step named |
Also part of this pathway
These proteins are described under another pathway, but also take part here.
| Protein | EC | Reaction (UniProt) | Metal or cluster | Amino acids | Certainty |
|---|---|---|---|---|---|
| 5,10-methylenetetrahydrofolate reductaseHome: Folate and pterin chemistry | 1.5.1.54 | (6S)-5-methyl-5,6,7,8-tetrahydrofolate + NAD(+) = (6R)-5,10-methylene-5,6,7,8-tetrahydrofolate + NADH + H(+) | — | 296 | Step named |
| Bifunctional protein FolDHome: Folate and pterin chemistry | 1.5.1.5; 3.5.4.9 | (6R)-5,10-methylene-5,6,7,8-tetrahydrofolate + NADP(+) = (6R)-5,10-methenyltetrahydrofolate + NADPH | — | 291 | Step named |
| Probable glycine dehydrogenase (decarboxylating) subunit 2Home: Folate-linked carbon transfer | 1.4.4.2 | N(6)-[(R)-lipoyl]-L-lysyl-[glycine-cleavage complex H protein] + glycine + H(+) = N(6)-[(R)-S(8)-aminomethyldihydrolipoyl]-L-lysyl-[glycine-cleavage complex H protein] + CO2 | — | 482 | Step named |
Origins
How could single carbon atoms have been carried and added before folate existed?
How it was discovered
- 1940sFolate is first isolated, from green leaves, liver and yeast.Horton et al., Principles of Biochemistry, p. 291
None of the books searched describes a prebiotic route to folate or to its one-carbon chemistry.
Formyl-tetrahydrofolate supplies two of the carbon atoms of the purine ring, so making DNA and RNA letters depends on this cofactor. Folate itself is a complex molecule built by its own pathway.
From the books: Horton et al., Principles of Biochemistry, p. 291; Zubay, Origins of Life on Earth and in the Cosmos, p. 226.
The wider question for this part of the cell: origins for making the twenty amino acids.
Sources
- Atlas pathway grouping from the VF5 reference-genome system map (Deckert et al. 1998; Braakman & Smith 2014)
Other pathways in this group: Aromatic amino acids · Branched-chain amino acids · Aspartate-family branches · Nitrogen assimilation · RNA maturation · Arginine biosynthesis · Cysteine and methionine metabolism · Histidine metabolism · Lysine biosynthesis · Arginine and proline metabolism · Phenylalanine, tyrosine and tryptophan biosynthesis · Not yet placed in a pathway