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Ligand Binding Interactions Modulating the Substrate Specificity of Diamine Oxidase

Isoforms of copper and topaquinone dependent diamine oxidases are widely distributed in prokaryotic and eukaryotic organisms in which they are required for the metabolism of arginine and histidine derived biogenic amines. The enzymatically regulated flux of biogenic amines plays an integral role in metabolic and physiological activities of the cell including nucleic acid and protein synthesis, the immune response, and neurotransmission. The immediate products of polyamine degradation: aminoaldehydes, ammonia, and hydrogen peroxide are each uniquely cytotoxic and for these reasons modulation of the catalytic activity of diamine oxidases is a critical aspect of normal cellular function. The biogenic amine substrates of DAO each bind and dramatically alter the structure and properties of DNA, RNA, and heparins, which are themselves macromolecular ligands of DAO. Here we report the role these substrate and macromolecular binding interactions in tuning the substrate specificity and catalytic mechanism of diamine oxidase.