Title: Direct conversion of ferrous myeloperoxidase to compound II by hydrogen peroxide: an anaerobic stopped-flow study
Abstract: Myeloperoxidase (MPO) is one of the essential components of the antimicrobial systems of polymorphonuclear neutrophils. It is unique in having a globin-like standard reduction potential of the ferric/ferrous couple. Here, it is shown that ferrous MPO heterolytically cleaves hydrogen peroxide forming water and oxyferryl MPO (compound II). The two-electron oxidation reaction follows second-order kinetics with the apparent bimolecular rate constant being (6.8 ± 0.6) × 104 M−1 s−1 at pH 7.0. After depletion of (micromolar) H2O2 compound II slowly decays to ferric MPO, whereas upon addition of millimolar H2O2 to ferrous MPO, compound III (oxyperoxidase) is formed in a sequence of two reactions involving compound II formation and its direct reaction with H2O2, which also follows second-order kinetics [(78 ± 2) M−1 s−1 at pH 7.0]. It is discussed how these reactions contribute to the interconversion of compound II and compound III and could explain the catalase activity of MPO.
Publication Year: 2003
Publication Date: 2003-11-15
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
Access and Citation
Cited By Count: 37
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