A blue protein as an inactivating factor for nitrite reductase from Alcaligenes faecalis strain S-6

J Biochem. 1981 Feb;89(2):463-72. doi: 10.1093/oxfordjournals.jbchem.a133221.


A blue protein with a molecule weight of 12,000 containing 1 atom of type I Cu2+ was purified and crystallized from a denitrifying bacterium, Alcaligenes faecalis strain S-6, as an inactivating factor for copper-containing nitrite reductase of the same organism. Inactivation of the enzyme occurred when the enzyme was incubated aerobically with a catalytic amount of the blue protein in the presence of reducing agents such as cysteine and ascorbate. The blue protein acts as a direct electron donor for the enzyme to catalyze the reduction of nitrite, but in the absence of nitrite, the enzyme-reduced blue protein system reacts with oxygen to produce H2O2. A suicide inactivation mechanism of the enzyme due to this H2O2 production is proposed.

MeSH terms

  • Alcaligenes / enzymology*
  • Amino Acids / analysis
  • Bacterial Proteins*
  • Copper / analysis
  • Cysteine
  • Electron Spin Resonance Spectroscopy
  • Hydrogen Peroxide / pharmacology
  • Metalloproteins / isolation & purification
  • Metalloproteins / pharmacology*
  • NADH, NADPH Oxidoreductases / antagonists & inhibitors*
  • Nitrite Reductases / antagonists & inhibitors*
  • Oxidation-Reduction
  • Oxygen
  • Spectrum Analysis


  • Amino Acids
  • Bacterial Proteins
  • Metalloproteins
  • mauC protein, Methylobacterium extorquens
  • Copper
  • Hydrogen Peroxide
  • NADH, NADPH Oxidoreductases
  • Nitrite Reductases
  • Cysteine
  • Oxygen