This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
[{'content': 'H4-biopterin (tetrahydrobiopterin) is required for metabolism of \nSelect and explain. \nA. Arginine, B. Lysine, C. Phenylalanine, D. Tryptophane', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Conversion of phenylalanine to tyrosine: The reaction involves hydroxylation of phenylalanine at p-position in benzene ring. Enzyme: Phenylalanine hydroxylase. Present in liver and the conversion occurs in Liver. Coenzymes and cofactors: The enzyme requires the following for its activity: * Molecular oxygen * NADPH *F e++ and * Pteridine (folic acid) coenzyme: Tetrahydrobiopterin- FH4 The reaction is complex and takes place in two stages as shown below: I. Reduction of O2 to H2O and conversion of phenylalanine to tyrosine. Reduced form of pteridine, FH4 acts as H-donor to the molecular O2. II. Reduction of dihydrobiopterin, FH2 by NADPH, catalyzed by the enzyme Dihydrobiopterin reductase.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 495', 'role': 'assistant'}]