fenylalaninehydroxylase

Phenylalanine hydroxylase, often abbreviated as PAH, is an enzyme primarily found in the liver. Its main function is to catalyze the conversion of the amino acid phenylalanine to another amino acid, tyrosine. This reaction is a crucial step in the metabolic pathway of phenylalanine. PAH requires a cofactor, tetrahydrobiopterin (BH4), and iron as part of its catalytic activity. The enzyme's gene is located on chromosome 12 in humans. Mutations in the PAH gene are the cause of phenylketonuria (PKU), a genetic disorder. In individuals with PKU, the PAH enzyme is deficient or non-functional, leading to a buildup of phenylalanine in the blood. This accumulation can be toxic to the brain, especially during development, and can result in intellectual disability if left untreated. Treatment for PKU typically involves a strict low-phenylalanine diet. The understanding of PAH has been central to developing diagnostic tests and management strategies for PKU.