Reactions of plant copper/topaquinone amine oxidases with N6–aminoalkyl derivatives of adenine
PADIGLIA, ALESSANDRA;MEDDA, ROSARIA;
2005-01-01
Abstract
Plant copper/topaquinone-containing amine oxidases (CAOs, EC 1.4.3.6) are enzymes oxidising various amines. Here we report a study on the reactions of CAOs from grass pea (Lathyrus sativus), lentil (Lens esculenta) and Euphorbia characias, a Mediterranean shrub, with N6-aminoalkyl adenines representing combined analogues of cytokinins and polyamines. The following compounds were synthesised: N6-(3-aminopropyl)adenine, N6-(4-aminobutyl)adenine, N6-(4-amino-trans-but-2- enyl)adenine, N6-(4-amino-cis-but-2-enyl)adenine and N6-(4-aminobut-2-ynyl)adenine. From these, N 6-(4-aminobutyl) adenine and N6-(4-amino-trans-but-2-enyl)adenine were found to be substrates for all three enzymes ðKm , 1024MÞ: Absorption spectroscopy demonstrated such an interaction with the cofactor topaquinone, which is typical for common diamine substrates. However, only the former compound provided a regular reaction stoichiometry. Anaerobic absorption spectra of N6-(3-aminopropyl)adenine, N6-(4-amino-cis-but-2-enyl)adenine and N6-(4-aminobut-2-ynyl)adenine reactions revealed a similar kind of initial interaction, although the compounds finally inhibited the enzymes. Kinetic measurements allowed the determination of both inhibition type and strength; N 6-(3-aminopropyl)adenine and N6-(4-amino-cis-but-2- enyl)adenine produced reversible inhibition ðKi , 1025 –1024MÞ whereas, N 6-(4-aminobut-2-ynyl)adenine could be considered a powerful inactivator.Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.