ABSTRACT
Copper amine oxidases (CAOs; EC 1.4.3.6) contain a redox-active quinone cofactor covalently linked to their polypeptide chains: 2,4,5-trihydroxyphenylalanine quinone, abbreviated as TOPA quinone or TPQ. Because TPQ occurs as an integral amino acid residue of a polypeptide chain and is encoded as a Tyr residue in all genes coding for CAOs, a specic mechanism of post-translational modication must occur to generate TPQ from the precursor Tyr residue in the nascent polypeptide chain.
