Formate: The Neglected Member of One-Carbon Metabolism.

Formate, the only non-tetrahydrofolate (THF)-linked intermediate in one-carbon metabolism, is produced in mammals from a variety of metabolic sources. It occurs in serum of adults at a concentration of approximately 30 μM. Its principal function lies as a source of one-carbon groups for the synthesis of 10-formyl-THF and other one-carbon intermediates; these are primarily used for purine synthesis, thymidylate synthesis, and the provision of methyl groups for synthetic, regulatory, and epigenetic methylation reactions. Although formate is largely produced in mitochondria, these functions mostly occur in the cytoplasm and nucleus. Formate plays a significant role in embryonic development, as evidenced by the effectiveness of formate in the pregnant dam's drinking water on the incidence of neural tube defects in some genetic models. High formate concentrations in fetal lambs may indicate a role in fetal development and suggest that extracellular formate may play a role in the interorgan distribution of one-carbon groups.