Phenylketonuria (PKU) is a rare autosomal recessive condition characterized by an inability to metabolize the amino acid phenylalanine. The most common variation of PKU is associated with a mutation of the phenylalanine hydroxylase (PAH) gene, located on chromosome 12q. Individuals with PKU have an absence of or significant deficiency in the PAH enzyme. Functional PAH is necessary for the metabolism of phenylalanine into tyrosine, a precursor for the neurotransmitter dopamine. Disruption of this metabolic process results in higher-than-normal levels of phenylalanine as well as decreased tyrosine levels. The excessive phenylalanine further competes with the available tyrosine and other large neutral amino acids (LNAAs) to cross the blood-brain barrier, ultimately resulting in decreased synthesis of dopamine and other neurotransmitters within the brain.
References and Reading
- Blau, N. (Ed.). (2006). PKU and BH4: Advances in phenylketonuria and tetrahydrobiopterin. Heilbronn: SPS.Google Scholar