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
Melatonin is synthesised from 
Select and explain. 
A. Tryptophan, B. Serotonin, C. Phenyllanine, D. Histidine
A: Tryptophan
Answer: A: Tryptophan 
Explanation: 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