We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
The Mechanism of 2-Nitropropane Dioxygenase: a Model for Flavin Semiquinone Intermediates in Enzymatic Catalysis.
- Authors
Gadda, Giovanni; Francis, Kevin; Belaineh, Merid
- Abstract
2-Nitropropane dioxygenase (E.C.1.13.11.32) is an FMN-dependent enzyme that catalyzes the oxidation of nitroalkanes and nitronates to their corresponding carbonyl compounds and nitrite. Mechanistic studies using pH, solvent viscosity, substrate kinetic isotope effects and rapid-mixing techniques have been used to investigate the chemical mechanism of substrate oxidation in the reaction catalyzed by 2-nitropropane dioxygenase. The resulting data are consistent with a catalytic base, His-196 in the enzyme from Neurospora crassa, initiating the oxidative pathway by abstracting a proton from the α-carbon of the neutral substrate to generate an enzyme-bound alkylnitronate intermediate. This kinetic step is followed by a single electron transfer from the alkylnitronate to the enzyme-bound flavin that results in the transient formation of an anionic flavosemiquinone and a substrate radical. An electrostatic catalyst in the active site of the enzyme facilitates the formation of the anionic flavosemiquinone. After the flavin-linked one-electron reduction of molecular oxygen, the resulting superoxide reacts with the substrate radical generating a peroxynitroalkane intermediate before decaying to give the carbonyl product of the reaction. Catalysis with alkylnitronates as substrates proceeds in a similar fashion except that the initial proton abstraction step is excluded.
- Subjects
NITROPROPANE; FLAVINS; QUINONE; CATALYSIS; ENZYMES; NEUROSPORA crassa; 2-Nitropropane dioxygenase
- Publication
FASEB Journal, 2007, Vol 21, Issue 5, pA272
- ISSN
0892-6638
- Publication type
Article