Rapid reactions of peroxynitrite with heme-thiolate proteins as the basis for protection of prostacyclin synthase from inactivation by nitration

Arch Biochem Biophys. 2000 Apr 1;376(1):149-55. doi: 10.1006/abbi.2000.1699.


Prostacyclin (PGI(2)) synthase is a heme-thiolate (P450) protein which reacts with low levels of peroxynitrite (PN) under tyrosine nitration and inactivation. Studying heme proteins as models, we have found the heme-thiolate protein NADH-NO reductase (P450(NOR)) to be highly efficient in decomposing PN under concomitant nitration of phenol. The present study investigates two other P450 proteins, P450(BM-3) and chloroperoxidase, in order to test for the specific role of the thiolate ligand in the reaction with PN. A comparison with horseradish peroxidase and microperoxidase gives evidence of kinetic differences that classify heme-thiolate proteins, but not other heme proteins, as effective inhibitors of PGI(2) synthase nitration and inactivation. P450(BM-3) with PN catalyzes phenol nitration and nitration of its own tyrosine below 10 microM PN, whereas chloroperoxidase and P450(NOR) at such concentrations also nitrate phenol but not enzyme-bound tyrosine residues. We conclude that heme-thiolate proteins in general exhibit high reactivity with PN and turnover, probably due to the special electronic structure of the presumed thiolate-ferryl intermediate.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cytochrome P-450 Enzyme Inhibitors
  • Cytochrome P-450 Enzyme System / metabolism*
  • Hemeproteins / metabolism*
  • Horseradish Peroxidase / metabolism
  • Intramolecular Oxidoreductases / antagonists & inhibitors
  • Intramolecular Oxidoreductases / metabolism*
  • Kinetics
  • Models, Biological
  • Nitrates / metabolism*
  • Tyrosine / metabolism


  • Cytochrome P-450 Enzyme Inhibitors
  • Hemeproteins
  • Nitrates
  • peroxynitric acid
  • Tyrosine
  • Cytochrome P-450 Enzyme System
  • Horseradish Peroxidase
  • Intramolecular Oxidoreductases
  • prostacyclin synthetase