Nitric oxide covalently labels a 6-hydroxydopa-derived free radical intermediate in the catalytic cycle of copper/quinone-containing amine oxidase from lentil seedlings.
The reaction of NO-derivatized polyamines called "NONOates" with an amine oxidase from lentil seedlings was studied. 3,3-Bis(aminoethyl)-1-hydroxy-2-oxo-1-triazene (DETA-NONOate) and 3,3'-(hydroxynitrosohydrazino)bis-1-propanamine (DPTA-NONOate) were found to be irreversible inactivators of the lentil enzyme. The spectrum of the protein was strongly affected in the course of reaction with both compounds, leading to the formation of a covalent adduct with a stable band at 334 nm. The corresponding amine compounds diethylentriamine (DETA) and norspermidine (DPTA) were substrates of the lentil enzyme that did not lead to enzyme inactivation. Diethylamine-NONOate, not containing amino groups, was found to be an irreversible inactivator of the amine oxidase only in the presence of a substrate. Since all NONOates spontaneously decompose in solution with release of NO, it seems as if the latter is responsible for the enzyme inhibition. The insensitivity of the native enzyme to NO suggested that this compound was unreactive toward both the cofactors, 6-hydroxydopa quinone (TPQ) and Cu(II), and thus a model for the irreversible inactivation could involve the attack by NO of the Cu(I)-semiquinolamine radical catalytic intermediate.
Longu
Silvia
S
Department of Applied Sciences in Biosystems, University of Cagliari, I-09042 Monserrato, Cagliari, Italy.
Padiglia
Alessandra
A
Pedersen
Jens Z
JZ
Finazzi Agrò
Alessandro
A
Mura
Anna
A
Maccioni
Paola
P
Floris
Giovanni
G
Medda
Rosaria
R
D006631:Amine Oxidase (Copper-Containing) / Q000737:chemistry*; D016227:Benzoquinones / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D027806:Lens Plant / Q000201:enzymology*; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D010084:Oxidation-Reduction; D036226:Seedlings / Q000201:enzymology; D013997:Time Factors
D016227:Benzoquinones; D005609:Free Radicals; C001388:6-hydroxydopa; D009569:Nitric Oxide; C004532:quinone; D004295:Dihydroxyphenylalanine; D003300:Copper; D006631:Amine Oxidase (Copper-Containing)