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Micronutrient Information Center

Vitamin B12 and Nucleic Acid Metabolism

5,10-Methylene tetrahydrofolate (TH4) is required for the synthesis of nucleic acids, while 5-methyl TH4 is required for the formation of methionine from homocysteine. Methionine, in the form of S-adenosylmethionine, is required for many biological methylation reactions, including DNA methylation. Methylene TH4 reductase is a flavin-dependent enzyme required to catalyze the reduction of 5,10-methylene TH4 to 5-methyl TH4.