Oneliner_1865

OneLiner

PKU is most commonly caused by a deficiency of phenylalanine hydroxylase, the first enzyme in the breakdown pathway for phenylalanine. Phenylalanine hydroxylase converts phenylalanine to tyrosine, and then tyrosine hydroxylase converts tyrosine to DOPA. Both of these enzymes require a cofactor called tetrahydrobiopterin (BH4), which is regenerated by the enzyme dihydrobiopterin reductase.