Phenylalanine and Tyrosine Metabolism Analysis in Heterozygotes for Phenylketonuria and in Healthy Individuals

Abstract Phenylketonuria (PKU) is an inherited metabolic disorder derived from a deficiency in the enzyme phenylalanine hydroxylase, which converts the amino acid phenylalanine (Phe) into tyrosine (Tyr). Here we aimed to examine the metabolism of Phe and Tyr in heterozygotes for PKU during fasting and after oral overload of Phe (25 mg/kg). Plasma concentration of Phe and Tyr and Phe2–Tyr ratio were determined under fasting condition or 30, 45, 60, and 90 minutes after Phe overload. The sample consisted of 50 participants: 23 heterozygotes for PKU (10 men and 13 women) and a control group of ...