Figure 1.

Schematic representation of THF production and C1 metabolism and their distribution in different compartments of the plant cell (adapted from Ravanel et al., 2001; Loizeau et al., 2008). Arrows and numbers represent enzymatic reactions. Dashed arrows and gray squares represent folate transport and transporters, respectively. 1, Dihydrofolate reductase/thymidylate synthase; 2, folylpolyglutamate synthetase (AtDFB, AtDFC, and AtDFD); 3, Ser hydroxymethyltransferase; 4, Gly decarboxylase; 5, 5,10-CH₂-THF dehydrogenase/5,10-CH-THF cyclohydrolase; 6, 10-formyl-THF deformylase; 7, 5-formyl-THF cycloligase; 8, methionyl-tRNA formyltransferase; 9, Met synthase; 10, glycinamide ribonucleotide transformylase and aminoimidazole carboxamide ribonucleotide transformylase; 11, 5,10-CH₂-THF reductase; 12, AdoMet synthetase; 13, Met S-methyltransferase; 14, S-adenosylhomocysteine hydrolase; 15, ketopantoate hydroxymethyltransferase; 16, 10-formyl-THF synthetase.