Which of the following metabolic reactions require vitami 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. (Ref: KDT 6/e p588) Conversion of malonic acid to succinic acid requires vitamin B12 but not folate. This reaction is required for myelin formation and deficiency of B12 is responsible for demyelination.