Figure 1From: Genes and primary headaches: discovering new potential therapeutic targets Production of homocysteine as part of the amino acid and purine biosynthesis pathway. DHF = dihydrofolate, THF = tetrahydrofolate, MTHFR = methylene-tetrahydrofolate-reductase, TS = thymidylate-synthase, MTR = methionine-synthase, MTRR o MSR = methionine-synthase-reductase.Back to article page