This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Metabolites of tryptophan can give rise to all of the following except 
Select and explain. 
A. Diarrhoea, B. Vasoconstriction, C. Flushing, D. Phenylketonuria
D: Phenylketonuria
Answer: D: Phenylketonuria 
Explanation: Phenylketouria is due to deficiency of phenylalanine hydroxylase enzyme. This enzyme catalyzes hydroxylation of aromatic side chain of phenylalanine to generate tyrosine.
The conversation of phenylalanine to tyrosine is blocked resulting in the excretion of high amounts of PHENYLPYRUVATE in urine.
Clinical features:- mental retardation , failure to talk or walk , seizures, tremors.