Fig. (1) Homocysteine-Folate Pathway: The metabolic interactions between folate, methionine and homocysteine are shown here. Folate from the diet is absorbed and converted to methylenetetrahydrofolate (MTHF) with the formation of high-energy phosphate bonds by the action of MTHF reductase (MTHFR), methyl tetrahydrofolate is yielded which methylates homocysteine to methionine. Methionine is converted to SAM, the universal methyl donor. SAM provides methyl groups for several nucleic acid methylation reactions and gets reduced to S-adenosylhomocysteine which then reforms homocysteine and reinitiates the cycle. Abbreviations: SAM; S-adenosylmethionine, SAH; S-adenosylhomocysteine, MTHFR; methylenetetrahydrofolate reductase; B6 and B12; Vitamin B6 and Vitamin 12 respectively.