Figure 3.
In the folate-dependent, one-carbon metabolism, the 5MTHF provides methyl groups to the S-adenosylmethionine (SAMe, SAM) cycle through homocysteine (Hcy) conversion to methionine. SAMe is the primary methyl donor to the methyl groups in the body and is required in the methylation of a diverse number of targets, including phospholipids, DNA, ribonucleic acid, neurotransmitters, and proteins. Hcy is a byproduct of the one-carbon cycle and is accumulated in the bloodstream when it can’t be remethylated to methionine. Plasma Hcy levels are an indirect indicator of folate levels.18
Abbreviations: 5MTHF, 5-methyltetrahydrofolate; DHF, dihydrofolate; SAH, S adenosylhomocysteine; THF, tetrahydrofolate.