Reactions of plant copper/topaquinone amine oxidases with N 6 -aminoalkyl derivatives of adenine

Author： Lamplot Zbyněk Šebela Marek Fryčák Petr Longu Silvia Padiglia Alessandra Medda Rosaria Floris Giovanni Peč Pavel

Publisher： Informa Healthcare

ISSN： 1475-6366

Source： Journal of Enzyme Inhibition and Medicinal Chemistry, Vol.20, Iss.2, 2005-04, pp. : 143-151

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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 N 6 -aminoalkyl adenines representing combined analogues of cytokinins and polyamines. The following compounds were synthesised: N 6 -(3-aminopropyl)adenine, N 6 -(4-aminobutyl)adenine, N 6 -(4-amino-trans-but-2-enyl)adenine, N 6 -(4-amino-cis-but-2-enyl)adenine and N 6 -(4-aminobut-2-ynyl)adenine. From these, N 6 -(4-aminobutyl)adenine and N 6 -(4-amino-trans-but-2-enyl)adenine were found to be substrates for all three enzymes (Km~10 -4 ?M). 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 N 6 -(3-aminopropyl)adenine, N 6 -(4-amino-cis-but-2-enyl)adenine and N 6 -(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 N 6 -(4-amino-cis-but-2-enyl)adenine produced reversible inhibition (Ki~10 -5 –10 -4 ?M) whereas, N 6 -(4-aminobut-2-ynyl)adenine could be considered a powerful inactivator.