Amine oxidases from Aspergillus niger: identification of a novel flavin-dependent enzyme

Upon induction with various amine sources, two different amine oxidases are expressed in the filamentous fungus Aspergillus niger. The enzymes which can be separated by anion exchange chromatography exhibit a similar substrate specificity pattern. From cofactor and inhibitor analysis it was found that one amine oxidase is identical to the earlier reported copper-containing amine oxidase (Yamada, H., Adachi, O. and Ogata, K. (1965) Agric. Biol. Chem. 29, 912-917) with 6-hydroxydopa (TOPA) quinone as the active site cofactor. The second form is a hitherto unknown flavoprotein of 55 kDa, which shows many of the characteristic properties of the mammalian monoamine oxidases (MAO). From substrate specificity and inhibitor susceptibility, it is suggested that the monoamine oxidase from A. niger (MAO-N) is a prototype of the two mammalian enzymes, MAO-A and MAO-B. A partial cDNA clone which encodes an amino-terminal peptide of 53 amino acid residues was identified by lambda gt11 immunoscreening. The consensus sequence of the putative flavin adenine dinucleotide (FAD) binding site is found within this sequence.