Interaction of plant amine oxidases with diaminoethers

Polyamines are ubiquitous compounds, which are involved in crucial physiological events including cell growth and differentiation. The catabolic oxidative degradation of polyamines is catalyzed by quinoprotein copper-containing amine oxidases (CAOs) and flavoprotein polyamine oxidases (PAOs). Various synthetic polyamine analogs and polyamine derivatives have been reported, which represent important tools (substrates or inhibitors) in the study of catalytic properties of the enzymes. In this work, two related compounds were studied in the reactions with plant amine oxidases: 1,8-diamino-3,6-dioxaoctane (DADO) and 1,10-bis(2- pyridinylmethyl)-4,7-dioxa-1,10-diazadecane (BPDD). Based on activity and stoichiometry assays together with spectrophotometric measurements, DADO can be considered a good substrate for grass pea, lentil and E. characias CAOs with Km values in the range 10-4 – 10-3 M. Its oxidative degradation produces the corresponding aminoaldehyde 8-amino-3,6-dioxaoctanal, which does not undergo spontaneous cyclization (as it is known for the oxidation products of natural substrates putrescine, cadaverine and spermidine) or polymerization in the reaction mixture. Conversely, oat PAO does not oxidize DADO and is only weakly inhibited by the compound (Ki = 1.6 mM towards putrescine). BPDD was found to be a competitive inhibitor of both CAOs and PAOs with Ki values of 10-4 M. DADO could be suggested as a potential affinity ligand for CAOs