Figure 4.

Cross-talk between one-carbon metabolism and Levodopa catabolism. Diagram depicting the effects of dopamine metabolism on the one-carbon metabolic pathway. Conversion of levodopa to dopamine requires the breakage of S-adenosyl methionine as methyl group donor which is the same source of methyl groups used by DNA methyltransferases (DNMTs) to methylation cytosine residues. In addition, homocysteine produced by the conversion levodopa-dopamine is an inhibitor of DNMTs activity and may alter DNA methylation. COMT further mediates the conversion of dopamine into O-methyl derivatives (3-methoxytyramine) by consuming methyl groups from SAM. The potential interaction with PD medication is indicated, with Sinemet and Stalevo increasing levodopa levels and COMTAN inhibiting COMT activity.