This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Structure & Function of Proteins), Subject name: Biochemistry
Cofactor involve in sulphur containing amino acid metabolism is? 
Select and explain. 
A. Folic acid, B. Biotin, C. Vitamin B 1, D. Vitamin B 12
D: Vitamin B 12
Answer: D: Vitamin B 12 
Explanation: ANSWER: (D) Vitamin B 12REF: Lehninger Principles of Biochemistry 4tR edition page 674Sulphur conatining amino acids are methionine, cystine and cysteineVitamin B 12 is a co-factor for methionine synthetase; it helps to convert homocysteine to methionine