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. (C) 2003 Elsevier Science B.V All rights reserved.