Comparison of Coupling Subsites and Inhibition Effects of Piperidine Alkaloids and Aminoketones on Plant Amine Oxidases

Abstract

In the present work we compare the binding subsites of inhibitors from a series of alkaloids and aminoketones on pea and sainfoin diamine oridase (EC 1.4.3.6; DAO) by the graphical method. As standard competitive inhibitors we have chosen oxoanalogs of the substrates, namely. 1.4-diamino-2-butanone and 1.5-diamino-3-pentanone, which were compared with the alkaloids (+)-sedamine. (-)-norallosedamine, (-)-nonedamhe, L-lobeline, cinchonine and aromatic analogs of aliphatic aminoketones such as l-amino-3-phenyl-3-propanone and l-amino-3-phenyl-2-propanone. In the case of pea DAO all inhibitors compete for the same subsites with 1,4-diamino-2-butanone and 1,5-diamino-3-pentanone (α = ∞). In the case of sainfoin enzyme they are bound to otheir subsites and the interaction constants (0 <α < 1) point to a positive attraction between these two types of inhibitors. With sainfoin DAO, l-amino-3-phenyl-3-propanone is bound into the same subsite as 1,4-diamino-2-butanone. Cinchonine and l-amino-3-phenyl-3-propanone are bound to two different subsites and the value of the interaction constant (1 < α < ∞) shows repulsion between the inhibitors.

Key Words: :

• Diamine oxidase
• competitive inhibitors
• alkaloids
• examining overlapping subsites