The review paper deals with the contemporary theoretical knowledge about the role of Cu-amino- oxidase in the biosynthesis of alkaloids in plants. In the biosynthesis of tropane and piperidine alkaloids, aminooxidase participates in the conversion of amines into aldehydes which are the first important intermediates in the biosynthesis of these alkaloids. Norkoklaurine, the precursor of benzylisoquinoline alkaloids, is formed by condensation of dopamine and tyral. In the biosynthesis of benzylisoquinoline alkaloids of protoberberine and berberine type, tyral, the aldehyde condensa- tion unit, is produced by the action of aminooxidase. In morphinan alkaloids, the catalytic role of aminooxidase in the formation of tyral have not been demonstrated yet. The paper pays special attention to the mechanism of the aminooxidase-catalyzed reaction, the structure of the active site of the enzyme, and the molecular-biological properties of Cu-aminooxidases.

        Key words: aminooxidase – benzylisoquinoline alkaloids – aldehyde-condensing unit – amino-condensing unit