This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Phenylalanine and Tyrosine metabolism Detail, Subject name: Biochemistry
[{'content': 'In Phenylketonuria, the first line therapy is: \nSelect and explain. \nA. Replacement of the defective enzyme, B. Replacement of the deficient product, C. Limiting the substrate for deficient enzyme, D. Giving the missing amino acid by diet', 'role': 'user'}, {'content': 'Answer: C \nExplanation: In phenylketonuria:- There is accumulation of phenylalanine Accumulated phenylalanine inhibits the transpo of other amino acids required for neurotransmitter synthesis, reduces synthesis and increases degradation of myelin - Mental retardation Breastfeeding introduces phenylalanine and symptoms will be:- 1. Vomiting 2. Irritability 3. Convulsions & tremors are the usual presentations. Thus, limiting the substrate of the deficient enzyme, i.e. phenylalanine, is the first-line of management. Breastfeeding should be avoided.', 'role': 'assistant'}]