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Updated: May 6, 2026

Fast and Specific Assessment of the Halogenating Peroxidase Activity in Leukocyte-enriched Blood Samples
Published on: July 28, 2016
Oxidation of methionine by human polymorphonuclear leukocytes
Phagocytosing neutrophils oxidize methionine via the myeloperoxidase system, potentially involving singlet oxygen. This process may contribute to how neutrophils damage microbes.
Area of Science:
- Biochemistry
- Immunology
- Cell Biology
Background:
- Singlet oxygen ((1)O(2)) mediates photosensitized oxidation of methionine.
- Human polymorphonuclear leukocytes (PMN) are key immune cells involved in microbial defense.
Purpose of the Study:
- To investigate the mechanism by which phagocytosing PMN oxidize methionine.
- To determine the role of singlet oxygen and the myeloperoxidase (MPO) system in this process.
Main Methods:
- Incubation of human PMN with methionine under various conditions.
- Use of N-ethylmaleimide, (1)O(2) quenchers, MPO inhibitors, superoxide dismutase, catalase, and deuterium oxide.
- Analysis of methionine oxidation to methionine sulfoxide.
- Experiments with neutrophils from chronic granulomatous disease patients and isolated PMN fractions.
Main Results:
- Phagocytosing PMN, but not resting PMN, oxidized methionine.
- Oxidation was inhibited by (1)O(2) quenchers, MPO inhibitors, and catalase, but not by superoxide dismutase.
- Deuterium oxide significantly stimulated methionine oxidation.
- The MPO-H(2)O(2)-Cl(-) system was implicated in methionine oxidation by PMN granular fractions.
Conclusions:
- Methionine oxidation by phagocytosing PMN is dependent on the MPO-mediated antimicrobial system.
- Singlet oxygen likely mediates methionine oxidation, although not definitively proven.
- Methionine oxidation may be a mechanism by which PMN damage microorganisms.
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