This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
[{'content': 'Tyrosine is required for the synthesis of all of the following except: \nSelect and explain. \nA. Melatonin, B. Epinephrine, C. Norepinephrine, D. Thyroxine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A. MelatoninMelatonin is a hormone, synthesized by pineal gland. The amino acid required is tryptophan. It is also called N-acetyl 5- methoxy serotonin. Melatonin is involved in circadian rhythms.Epinephrine, Nor-epinephrine and thyroxine are all synthesized by Tyrosine.', 'role': 'assistant'}]