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Micronutrient Information Center

Involvement of B Vitamins in Homocysteine Metabolism

S-adenosyl homocysteine is formed during S-adenosyl methionine-dependent methylation reactions, and the hydrolysis of S-adenosyl homocysteine results in homocysteine. Homocysteine may be remethylated to form methionine in a reaction that requires both folate and vitamin B12. Alternately, homocysteine may be metabolized to the amino acid, cysteine, in reactions catalyzed by two vitamin B6-dependent enzymes.