Reactions of plant copper/topaquinone amine oxidases with N6-aminoalkyl derivatives of adenine.
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, N6-(4-aminobutyl) adenine and N6-(4-amino-trans-but-2-enyl)adenine were found to be substrates for all three enzymes (Km approximately 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 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; N6-(3-aminopropyl)adenine and N6-(4-amino-cis-but-2-enyl)adenine produced reversible inhibition (Ki approximately 10(-5) - 10(-4) M) whereas, N6-(4-aminobut-2-ynyl)adenine could be considered a powerful inactivator.
Lamplot
Zbynĕk
Z
Department of Biochemistry, Faculty of Science, Palacký University, Slechtitelu 11, CZ-783 71 Olomouc, Czech Republic.
Sebela
Marek
M
Frycák
Petr
P
Longu
Silvia
S
Padiglia
Alessandra
A
Medda
Rosaria
R
Floris
Giovanni
G
Pec
Pavel
P
D000225:Adenine / Q000031:analogs & derivatives / Q000737:chemistry*; D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry / Q000494:pharmacology*; D003583:Cytokinins / Q000737:chemistry / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D027806:Lens Plant; D008956:Models, Chemical; D018532:Pisum sativum; D010936:Plant Extracts; D010944:Plants / Q000378:metabolism; D010946:Plants, Medicinal / Q000378:metabolism; D013053:Spectrophotometry; D013379:Substrate Specificity; D013696:Temperature
D003583:Cytokinins; D004791:Enzyme Inhibitors; D010936:Plant Extracts; D004295:Dihydroxyphenylalanine; C067626:6-hydroxydopa quinone; D006631:Amine Oxidase (Copper-Containing); D000225:Adenine