In using dietary restriction of phenylalanine to manage a 2-month-old girl who has phenylketonuria, which of the following should be added to the diet?

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Quizplus · Accepted Answer

Tyrosine should be added to the diet because in phenylketonuria, the conversion of phenylalanine to tyrosine is impaired, making tyrosine an essential amino acid for these patients. A deficiency in phenylalanine hydroxylase (PAH) is the cause of PKU. Tyrosine is produced in cells by hydroxylating the essential amino acid phenylalanine and this reaction is catalyzed by PAH. Half of the phenylalanine required goes into the production of tyrosine; if the diet is rich in tyrosine itself, the requirements for phenylalanine are reduced by about 50%

In Using Dietary Restriction of Phenylalanine to Manage a 2-Month-Old