Anti-Phenylalanine Hydroxylase antibodies are used in the immunodetection of the protein encoded by the PAH gene. In humans, the canonical protein has a reported length of 452 amino acid residues and a mass of 51.9 kDa. A member of the Biopterin-dependent aromatic amino acid hydroxylase protein family, it is known to catalyze the hydroxylation of L-phenylalanine to L-tyrosine. Post-translational modifications have been described, including phosphorylation. Other names for this target antigen include PKU, PKU1, phenylalanine-4-hydroxylase, phe-4-monooxygenase, phenylalanine 4-monooxygenase, and PH.