The multi-functional topa-quinone copper amine oxidases.

The mature copper amine oxidases (CAOs) contain a tyrosine-derived 2,4,5-trihydroxyphenylalanyl quinone (topa quinone or TPQ) and a cupric ion in close proximity. Through a combination of structural, spectroscopic and kinetic analyses, a chemical mechanism for the self-processing of an active site tyrosine to TPQ has been proposed. Once formed, TPQ acts as a switch between the heterolytic transformation of amine substrates to aldehydes, via a pyridoxal phosphate-like Schiff base complex, and one electron chemistry involving reduction of molecular oxygen. The relationship between the biogenetic and catalytic processes is discussed.