Copper containing amine oxidases represent a major experimental challenge with regard to the identity of a covalently bound cofactor, the role of active site copper and chemical mechanism. Recent evidence suggests that bovine plasma amine oxidase (BPAO) may contain pyrroloquinoline quinone, a new redox cofactor hitherto seen exclusively in prokaryotes. The goals of this proposal to obtain characterization a detailed of structure and mechanism in BPAO with the expectation that such studies will expand our knowledge of the general class of copper amine oxidases. Our work will focus on four areas: (I) Structure of the organic cofactor; (II) Substrate-cofactor interactions; (III) Active site copper; and (IV) Relationship among pro-and eukaryotic enzymes containing pyrroloquinoline quinone