title: The inhibitory effect of acetaminophen on the myeloperoxidase-induced antimicrobial system of the polymorphonuclear leukocyte.
abstract: Acetaminophen binds via its acetamido side chain to purified myeloperoxidase in a pH-dependent manner and maximum binding occurred around pH 6. The H2O2-dependent myeloperoxidase-catalysed polymerization products of acetaminophen had excitation maxima at 304 nm and 334 nm in acid and alkaline solutions, respectively, and an intense blue fluorescence maximum at 426 nm. Acetaminophen can compete effectively with Cl- as myeloperoxidase substrate and thus HOCl formation is suppressed while HOCl, nevertheless present, can be scavenged by the drug. In this way the microbicidal action of the myeloperoxidase-H2O2-Cl- system can be seriously limited in the presence of high concentrations of acetaminophen. To study the effect of acetaminophen on peptide bond splitting in the myeloperoxidase antimicrobial system, thyroglobulin was used as a model peptide. Peptide bond splitting was inhibited at acetaminophen concentrations below the accepted toxic range for plasma values.
authors.affiliation: Department of Pharmacology, Medical School, University of Stellenbosch, Tygerberg, South Africa.
authors.forename: J M
authors.initials: JM
authors.lastname: van Zyl
authors.forename: K
authors.initials: K
authors.lastname: Basson
authors.forename: B J
authors.initials: BJ
authors.lastname: van der Walt
mesh_terms: D000082:Acetaminophen / Q000494:pharmacology*; D001770:Blood Bactericidal Activity / Q000187:drug effects*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006997:Hypochlorous Acid / Q000378:metabolism* / Q000633:toxicity; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism*; D013954:Thyroglobulin / Q000378:metabolism
chemical_list: D000082:Acetaminophen; D006997:Hypochlorous Acid; D013954:Thyroglobulin; D009195:Peroxidase