This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Classification and metabolism of amino acids, Subject name: Biochemistry
[{'content': 'Precursor of tyrosine is: \nSelect and explain. \nA. Cysteine, B. Histidine, C. Tryptophan, D. Phenylalanine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Phenylalanine in the presence of phenylalanine hydroxylase forms tyrosine . So precursor for tyrosine is phenylalanine Extra Information: Enzyme Disease Phenylalanine hydroxylase Classical phenylketonuria or PKU-1 Dihydrobiopterin reductase Non-classical PKU type 2 & 3 GTP-Cyclo hydrolase Non-classical type 4 or 5', 'role': 'assistant'}]