1. Academic Validation
  2. 2-thioxanthines are mechanism-based inactivators of myeloperoxidase that block oxidative stress during inflammation

2-thioxanthines are mechanism-based inactivators of myeloperoxidase that block oxidative stress during inflammation

  • J Biol Chem. 2011 Oct 28;286(43):37578-89. doi: 10.1074/jbc.M111.266981.
Anna-Karin Tidén 1 Tove Sjögren Mats Svensson Alexandra Bernlind Revathy Senthilmohan Francoise Auchère Henrietta Norman Per-Olof Markgren Susanne Gustavsson Staffan Schmidt Stefan Lundquist Louisa V Forbes Nicholas J Magon Louise N Paton Guy N L Jameson Håkan Eriksson Anthony J Kettle
Affiliations

Affiliation

  • 1 AstraZeneca R&D, Södertälje SE-151 85, Sweden.
Abstract

Myeloperoxidase (MPO) is a prime candidate for promoting oxidative stress during inflammation. This abundant Enzyme of neutrophils uses hydrogen peroxide to oxidize chloride to highly reactive and toxic chlorine bleach. We have identified 2-thioxanthines as potent mechanism-based inactivators of MPO. Mass spectrometry and x-ray crystal structures revealed that these inhibitors become covalently attached to the heme prosthetic groups of the Enzyme. We propose a mechanism whereby 2-thioxanthines are oxidized, and their incipient free radicals react with the heme groups of the Enzyme before they can exit the active site. 2-Thioxanthines inhibited MPO in plasma and decreased protein chlorination in a mouse model of peritonitis. They slowed but did not prevent neutrophils from killing bacteria and were poor inhibitors of thyroid peroxidase. Our study shows that MPO is susceptible to the free radicals it generates, and this Achilles' heel of the Enzyme can be exploited to block oxidative stress during inflammation.

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