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Simplified schematic diagram of the folate cycle

The folate cycle is actually more than one set of cyclic biochemical interconversions involving metabolites of folate. This illustration also shows the close relationship of the folate cycle to the methionine remethylation cycle and the trans-sulfuration pathway.

Legend: 5-MTHF: 5-methyl-tetrahydrofolate; 5,10-MTHF: 5,10-methyl-tetrahydrofolate; BHMT: betaine-homocysteine S-methyltransferase; CBS: cystathionine beta synthase; CGL: cystathionine gamma-lyase; DHF: dihydrofolate (vitamin B9); DMG: dimethylglycine; dTMP: thymidine monophosphate; dUMP: deoxyuridine monophosphate; FAD+: flavine adenine dinucleotide; FTHF: 10-formyltetrahydrofolate; MS: methionine synthase; MTHFR: methylenetetrahydrofolate reductase; SAH: S-adenosyl-L-homocysteine; SAM: S-adenosyl-L-methionine; THF: tetrahydrofolate. (Original by Guillaume Pelletier, March 25, 2014. Modified by Dr. Douglas Lanska. Creative Commons Attribution-Share Alike 3.0 Unported license.)