A new born infant is diagnosed with phenylketonuria. The enzyme that is deficient is

Phenylketonuria is a disorder of phenylalanine metabolism and occurs due to deficiency of phenylalanine hydroxylase.It is a recessive condition.Here,phenylalanine could not be conveed to tyrosine,so phenylalanine accumulates and alternate minor pathways are opened to produce and excrete phenylketone(phenyl pyruvate),phenyl lactate and phenyl acetate in urine. Phenylalanine hydroxylase is an enzyme your body uses to conve phenylalanine into tyrosine, which your body needs to create neurotransmitters such as epinephrine, norepinephrine, and dopamine. PKU is caused by a defect in the gene that helps create phenylalanine hydroxylase. When this enzyme is missing, your body can't break down phenylalanine. This causes a buildup of phenylalanine in your body. Reference:Essential pediatrics-Ghai,8th edition,page no:652;Textbook of biochemistry-DM Vasudevan,6th edition,page no:207