title: Nitrite and nitroso compounds can serve as specific catalase inhibitors.
abstract: OBJECTIVE
  We present evidence that nitrite and nitrosothiols, nitrosoamines and non-heme dinitrosyl iron complexes can reversibly inhibit catalase with equal effectiveness.
  
  
  METHODS
  Catalase activity was evaluated by the permanganatometric and calorimetric assays.
  
  
  RESULTS
  This inhibition is not the result of chemical transformations of these compounds to a single inhibitor, as well as it is not the result of NO release from these substances (as NO traps have no effect on the extent of inhibition). It was found that chloride and bromide in concentration above 80 mM and thiocyanate in concentration above 20 μM enhance catalase inhibition by nitrite and the nitroso compounds more than 100 times. The inhibition degree in this case is comparable with that induced by azide.
  
  
  CONCLUSIONS
  We propose that the direct catalase inhibitor is a positively charged NO-group. This group acquires a positive charge in the active center of enzyme by interaction of nitrite or nitroso compounds with some enzyme groups. Halides and thiocyanate protect the NO+group from hydration and thus increase its inhibition effect. It is probable that a comparatively low chloride concentration in many cells is the main factor to protect catalase from inhibition by nitrite and nitroso compounds.
authors.affiliation: a NI Pirogov Russian National Research Medical University , 1 Ostrovityanov St, 117997 Moscow , Russia.
authors.forename: Vladimir Yu
authors.initials: VY
authors.lastname: Titov
authors.affiliation: a NI Pirogov Russian National Research Medical University , 1 Ostrovityanov St, 117997 Moscow , Russia.
authors.forename: Anatoly N
authors.initials: AN
authors.lastname: Osipov
mesh_terms: D002151:Calorimetry / Q000379:methods; D002374:Catalase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000737:chemistry / Q000494:pharmacology; D009573:Nitrites / Q000737:chemistry / Q000494:pharmacology*; D009589:Nitrogen Oxides / Q000737:chemistry / Q000494:pharmacology; D009603:Nitroso Compounds / Q000737:chemistry / Q000494:pharmacology*; D026403:S-Nitrosothiols / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D009573:Nitrites; D009589:Nitrogen Oxides; D009603:Nitroso Compounds; D026403:S-Nitrosothiols; C073661:dinitrosyl iron complex; D007501:Iron; D002374:Catalase
keywords: Catalase; Dinitrosyl iron complex; Haem-containing peroxidase; Halide ions; Inhibition; Nitrite; S-nitrosothiols; Thiocyanate