Metabolic folate pathway. Metabolites: 5-MeTHF indicates 5-methyltetrahydrofolate; 10-formyl THF, 10-formyltetrahydrofolate; SAM, adenosylmethionine; SAH, S-adenosylhomocysteine; DHF, dihydrofolate; THF, tetrahydrofolate; dTMP, deoxythymidine monophosphate; and dUMP, deoxyuridine monophosphate. Enzymes: MTR indicates methionine synthase; SHMT, serine hydroxymethyltransferase; MTHFR, 5,10-methylenetetrahydrofolate reductase; and TS, thymidylate synthase.