Electroreduction of nitrite to nitrogen oxide by a copper-containing nitrite reductase model complex incorporated into collagen film.
The electrocatalytic reduction of nitrite to NO by CuMe(2)bpaCl(2), which is a model for the active site of copper-containing nitrite reductase, incorporated into collagen film was investigated. The 77-K EPR spectrum of CuMe(2)bpaCl(2) in the collagen matrix revealed the typical axial signals (g(//)=2.26, g( perpendicular)=2.05, A(//)=16.4mT) of a tetragonal Cu(2+) chromophore. The redox potential, which is related to the Cu(+)/Cu(2+) couple, was -63mV (E=72mV) at pH 5.5. In the presence of nitrite, an increase in the cathodic current was observed in the cyclic voltammogram of CuMe(2)bpaCl(2) in the collagen matrix. Upon reaching -300mV, a linear generation of NO was observed for the CuMe(2)bpaCl(2)/collagen film-coated electrode. The relationship between the rate of NO generation and the nitrite concentration in solution was analyzed using the Michaelis-Menten equation, where V(max)=3.16nM s(-1) and K(m)=1.1mM at pH 5.5. The current increase and the reaction rate were dependent on the pH of the solution. The mechanism of nitrite reduction by the copper complex in the collagen matrix was the same mechanism as that of the enzyme in aqueous solution.
Isoda
Naoko
N
Department of Chemistry, Osaka University, Toyonaka, Japan.
Yokoyama
Hiroshi
H
Nojiri
Masaki
M
Suzuki
Shinnichiro
S
Yamaguchi
Kazuya
K
D055162:Biocatalysis; D003094:Collagen / Q000737:chemistry*; D004563:Electrochemistry; D004566:Electrodes; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008956:Models, Chemical; D009570:Nitriles / Q000737:chemistry*; D009572:Nitrite Reductases / Q000737:chemistry / Q000378:metabolism*; D009589:Nitrogen Oxides / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry; D010084:Oxidation-Reduction; D012996:Solutions / Q000737:chemistry
D009570:Nitriles; D009589:Nitrogen Oxides; D009942:Organometallic Compounds; D012996:Solutions; D003094:Collagen; D009572:Nitrite Reductases; C052695:nitrite reductase, copper-containing