Inborn errors of Phenylalanine metabolism: Phenylketonuria

    Phenylketonuria (PKU) is a metabolic disease characterized by accumulation of Phenylalanine (Phe) and its by-products in the blood of fetuses and newborns. PKU results from a defect in the enzyme Phenylalanine Hydroxylase (PAH), such that Phe is not converted to Tyrosine. The alternative conversion of Phe to PPA causes accumulation of the latter as a toxin in the Central Nervous System, which can lead to severe mental retardation.