Oxidized elafin and trappin poorly inhibit the elastolytic activity of neutrophil elastase and proteinase 3

FEBS J. 2005 Nov;272(22):5883-93. doi: 10.1111/j.1742-4658.2005.04988.x.


Neutrophil proteinase-mediated lung tissue destruction is prevented by inhibitors, including elafin and its precursor, trappin. We wanted to establish whether neutrophil-derived oxidants might impair the inhibitory function of these molecules. Myeloperoxidase/H(2)O(2) and N-chlorosuccinimide oxidation of the inhibitors was checked by mass spectrometry and enzymatic methods. Oxidation significantly lowers the affinities of the two inhibitors for neutrophil elastase (NE) and proteinase 3 (Pr3). This decrease in affinity is essentially caused by an increase in the rate of inhibitory complex dissociation. Oxidized elafin and trappin have, however, reasonable affinities for NE (K(i) = 4.0-9.2 x 10(-9) M) and for Pr3 (K(i) = 2.5-5.0 x 10(-8) M). These affinities are theoretically sufficient to allow the oxidized inhibitors to form tight binding complexes with NE and Pr3 in lung secretions where their physiological concentrations are in the micromolar range. Yet, they are unable to efficiently inhibit the elastolytic activity of the two enzymes. At their physiological concentration, fully oxidized elafin and trappin do not inhibit more than 30% of an equimolar concentration of NE or Pr3. We conclude that in vivo oxidation of elafin and trappin strongly impairs their activity. Inhibitor-based therapy of inflammatory lung diseases must be carried out using oxidation-resistant variants of these molecules.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Elafin
  • Enzyme Inhibitors / chemistry
  • Enzyme Inhibitors / pharmacology*
  • Enzyme Precursors / chemistry
  • Enzyme Precursors / genetics
  • Enzyme Precursors / pharmacology*
  • Genetic Variation
  • Humans
  • Kinetics
  • Leukocyte Elastase / antagonists & inhibitors*
  • Leukocyte Elastase / metabolism
  • Mass Spectrometry
  • Methionine / metabolism
  • Myeloblastin
  • Oxidation-Reduction
  • Protein Precursors / antagonists & inhibitors
  • Protein Precursors / metabolism
  • Proteinase Inhibitory Proteins, Secretory
  • Proteins / chemistry
  • Proteins / genetics
  • Proteins / pharmacology*
  • Recombinant Proteins / biosynthesis
  • Serine Endopeptidases / metabolism*


  • Elafin
  • Enzyme Inhibitors
  • Enzyme Precursors
  • PI3 protein, human
  • Protein Precursors
  • Proteinase Inhibitory Proteins, Secretory
  • Proteins
  • Recombinant Proteins
  • Methionine
  • Serine Endopeptidases
  • Leukocyte Elastase
  • Myeloblastin