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Interaction of myeloperoxidase with diclofenac. Inhibition of the chlorinating activity of myeloperoxidase by diclofenac and oxidation of diclofenac to dihydroxyazobenzene by myeloperoxidase. 1990

K W Zuurbier, and A R Bakkenist, and R H Fokkens, and N M Nibbering, and R Wever, and A O Muijsers
E.C. Slater Institute for Biochemical Research, University of Amsterdam, The Netherlands.

The chlorinating activity of myeloperoxidase, isolated from human polymorphonuclear neutrophils, was inhibited by the non-steroidal anti-inflammatory drug diclofenac (Voltaren). The concentration of diclofenac needed for 50% inhibition was 20 microM, a value comparable with IC50 values found for other drugs. Diclofenac did not react with HOCl nor with H2O2 but was oxidized in the presence of myeloperoxidase and H2O2 to an orange-coloured unstable product. The rate of oxidation was proportional to the enzyme concentration and to the concentration of diclofenac. but independent of the H2O2 concentration. Presumably both Compound I and Compound II, two intermediates formed during the reaction cycle of myeloperoxidase with H2O2 are able to oxidize diclofenac. In these redox reactions, the active short-living Compound I is reduced to Compound II, thereby inhibiting the chlorinating activity of the enzyme. Analysis by Fast Atom Bombardment mass spectrometry showed that in the presence of H2O2 myeloperoxidase oxidizes diclofenac to dihydroxyazobenzene.

UI MeSH Term Description Entries
D009195 Peroxidase A hemeprotein from leukocytes. Deficiency of this enzyme leads to a hereditary disorder coupled with disseminated moniliasis. It catalyzes the conversion of a donor and peroxide to an oxidized donor and water. EC 1.11.1.7. Myeloperoxidase,Hemi-Myeloperoxidase,Hemi Myeloperoxidase
D010084 Oxidation-Reduction A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471). Redox,Oxidation Reduction
D004008 Diclofenac A non-steroidal anti-inflammatory agent (NSAID) with antipyretic and analgesic actions. It is primarily available as the sodium salt. Diclophenac,Dichlofenal,Diclofenac Potassium,Diclofenac Sodium,Diclonate P,Dicrofenac,Feloran,GP-45,840,Novapirina,Orthofen,Orthophen,Ortofen,SR-38,Sodium Diclofenac,Voltaren,Voltarol,Diclofenac, Sodium,GP 45,840,GP45,840,SR 38,SR38
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D006861 Hydrogen Peroxide A strong oxidizing agent used in aqueous solution as a ripening agent, bleach, and topical anti-infective. It is relatively unstable and solutions deteriorate over time unless stabilized by the addition of acetanilide or similar organic materials. Hydrogen Peroxide (H2O2),Hydroperoxide,Oxydol,Perhydrol,Superoxol,Peroxide, Hydrogen
D001391 Azo Compounds Organic chemicals where aryl or alkyl groups are joined by two nitrogen atoms through a double bond (R-N Azo Dye,Azo Dyes,Compounds, Azo,Dye, Azo,Dyes, Azo
D013058 Mass Spectrometry An analytical method used in determining the identity of a chemical based on its mass using mass analyzers/mass spectrometers. Mass Spectroscopy,Spectrometry, Mass,Spectroscopy, Mass,Spectrum Analysis, Mass,Analysis, Mass Spectrum,Mass Spectrum Analysis,Analyses, Mass Spectrum,Mass Spectrum Analyses,Spectrum Analyses, Mass

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