Which of the following metabolic reactions require vitamin B12 but not folate?: (A) Conversion of malonic acid to succinic acid, (B) Conversion of homocysteine to methionine, (C) Conversion of serine to glycine, (D) Thymidylate synthesis
Answer is A. This reaction is required for myelin formation and deficiency of B12 is responsible for demyelination. Other reactions in question requires THFA in addition to Vit B12.