This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of protein and amino acid, Subject name: Biochemistry
[{'content': 'Melatonin is synthesised from \nSelect and explain. \nA. Tryptophan, B. Serotonin, C. Phenyllanine, D. Histidine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Tryptophan is conveed to Seratonin, which is acetylated. Fuher methylated with the help of S-adenosyl methionine to form Methionine.Ref: DM Vasudevan - Textbook of Biochemistry for Medical Students, 7th edition, page no: 241', 'role': 'assistant'}]