Whence topa? Models for the biogenesis of topa quinone in copper amine oxidases

Copper amine oxidases are dual function enzymes that first make their own cofactor, and then use this cofactor to catalyze amine oxidation. The cofactor, oxidized 2,4,5-trihydroxyphenylalanine (TPQ), is formed by the addition of cupric ion and dioxygen to precursor protein. Drawing on the mechanism of the oxidative half reaction in the copper amine oxidases, together with knowledge from other metal-containing enzyme systems, a new model is put forth for TPQ biogenesis.