[6] The electron-dense aromatic ring at position 403 may interact with amino groups in the substrate.
[7] Weak interactions with other more variable active site residues are involved in positioning the substrates.
Molecules downstream of polyamine oxidation play roles in cell proliferation.
Spermidine is a precursor to hypusine, which activates eukaryotic initiation factor 5A isoform 1 (eIF5A) that enables translation of mRNA.
[12] In plants, polyamine catabolism is tied closely to stress responses and fruit ripening.