Inhibition of lentil copper/TPQ amine oxidase by the mechanism-based inhibitor derived from tyramine.
Copper amine oxidase from lentil (Lens esculenta) seedlings was shown to catalyze the oxidative deamination of tyramine and three similar aromatic monoamines, benzylamine, phenylethylamine and 4-methoxyphenylethylamine. Tyramine, an important plant intermediate, was found to be both a substrate and an irreversible inhibitor of the enzyme whereas the other amines were not inhibitory. In the course of tyramine oxidation the enzyme gradually became inactivated with the concomitant appearance of a new absorption at 560 nm due to the formation of a stable adduct. Inactivation took place only in the presence of oxygen and was probably due to the reaction of the enzyme with the oxidation product of tyramine, p-hydroxyphenylacetaldehyde. The kinetic data obtained in this study indicate that tyramine represents a new interesting type of physiological mechanism-based inhibitor for plant copper amine oxidases.
Padiglia
Alessandra
A
Department of Applied Sciences in Biosystems, University of Cagliari, 1-09042 Monserrato, CA, Italy.
Floris
Giovanni
G
Longu
Silvia
S
Schininà
M Eugenia
ME
Pedersen
Jens Z
JZ
Finazzi Agrò
Alessandro
A
De Angelis
Francesco
F
Medda
Rosaria
R
D006631:Amine Oxidase (Copper-Containing) / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000302:isolation & purification; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000302:isolation & purification; D027806:Lens Plant / Q000201:enzymology*; D010936:Plant Extracts / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D036226:Seedlings; D014439:Tyramine / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*
C086758:2,4,5-trihydroxyphenylalanine quinone; D004791:Enzyme Inhibitors; D010936:Plant Extracts; D004295:Dihydroxyphenylalanine; C067626:6-hydroxydopa quinone; D006631:Amine Oxidase (Copper-Containing); D014439:Tyramine