Reactive nitrogen intermediates and antimicrobial activity: role of nitrite

Free Radic Biol Med. 1993 Apr;14(4):351-60. doi: 10.1016/0891-5849(93)90084-8.


The reactive nitrogen intermediate (RNI) nitric oxide (NO.) is formed from L-arginine by an NO. synthase and, following secondary reactions yielding additional toxic intermediates, nitrite (NO2-) and nitrate are formed. Nitrite, however, also has toxic properties. At acid pH, nitrous acid (HNO2) is bactericidal to Escherichia coli, in association with the loss of HNO2/NO2- and the uptake of oxygen, an effect which is increased by H2O2. Under conditions in which HNO2/NO2- +/- H2O2 were ineffective, the further addition of peroxidase (myeloperoxidase [MPO], eosinophil peroxidase, lactoperoxidase) or catalase resulted in bactericidal activity and the disappearance of HNO2/NO2-. Paradoxically, HNO2/NO2- also inhibited the bactericidal activity of MPO by the formation of a complex with MPO with a shift in the absorption spectrum, and by reaction with hypochlorous acid (HOCl) (the product of the chloride-supplemented MPO-H2O2 system), with loss of the bactericidal activity of HOCl and the disappearance of both HOCl and HNO2/NO2- from the reaction mixture. Thus, HNO2/NO2-, rather than being solely an end product of RNI formation, may influence antimicrobial activity either by acting alone, with H2O2, or with H2O2 and peroxidase as a source of toxic agents, or by inhibiting the peroxidase-mediated antimicrobial systems.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Eosinophil Peroxidase
  • Escherichia coli / drug effects*
  • Free Radicals
  • Glucose / pharmacology
  • Humans
  • Hydrogen Peroxide / metabolism
  • Hydrogen Peroxide / pharmacology
  • Hydrogen-Ion Concentration
  • In Vitro Techniques
  • Lactoperoxidase / metabolism
  • Nitrites / metabolism
  • Nitrites / pharmacology*
  • Nitrous Acid / metabolism
  • Nitrous Acid / pharmacology
  • Peroxidase / metabolism
  • Peroxidases / metabolism


  • Free Radicals
  • Nitrites
  • Hydrogen Peroxide
  • Eosinophil Peroxidase
  • Lactoperoxidase
  • Peroxidases
  • Peroxidase
  • Glucose
  • Nitrous Acid