Figure 1.

Summary of folate one-carbon metabolism showing the main pathways and reactions that have been subject to analysis in the context of NTDs. Blue shading: proteins involved in processing of folates in the digestive tract, transport and cellular retention (by addition of glutamates). Yellow shading: the major part of the cycle involving transfer of 1C groups between folate molecules, as required for purine and pyrimidine biosynthesis. Pink shading: reactions of the methylation cycle. For clarity, mitochondrial reactions that include generation of formate and cleavage of glycine have been omitted. For explanation of abbreviations, see Table 1.