title: Horseradish peroxidase-catalyzed oxidation of acetaminophen to intermediates that form polymers or conjugate with glutathione.
abstract: Horseradish peroxidase catalyzed the polymerization of acetaminophen. Addition of reduced glutathione (GSH) to reaction mixtures resulted in decreased polymerization and formation of minor amounts of GSH-acetaminophen conjugates. The conjugates were identified as 3-(glutathion-S-yl)acetaminophen and 3-(glutathion-S-yl)diacetaminophen. Horseradish peroxidase also catalyzed polymerization of synthetic 3-(glutathion-S-yl)acetaminophen to a dimer conjugate. In contrast to acetaminophen, 3-(glutathion-S-yl)acetaminophen oxidation was slowly catalyzed by horseradish peroxidase. However, in reaction mixtures containing equimolar concentrations of acetaminophen and synthetic 3-(glutathion-S-yl)acetaminophen, the formation of 3-(glutathion-S-yl)diacetaminophen and 3-(diglutathion-S-yl)diacetaminophen was rapid and accounted for approximately 95% of the products, whereas acetaminophen polymers accounted for only 5% of the products. These findings suggest that horseradish peroxidase catalyzed the one-electron oxidation of acetaminophen to N-acetyl-p-benzosemiquinone imine which preferentially polymerized rather than reacted with GSH. N-Acetyl-p-benzosemiquinone imine may also oxidize 3-(glutathion-S-yl)acetaminophen to form acetaminophen and 3-(glutathion-S-yl)-N-acetyl-p-benzosemiquinone imine. The data indicate that once this conjugate radical is formed it reacts with either N-acetyl-p-benzosemiquinone minine or 3-(glutathion-S-yl)-N-acetyl-p-benzosemiquinone imine via a radical termination mechanism.
mesh_terms: D000082:Acetaminophen / Q000031:analogs & derivatives*; D016227:Benzoquinones; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D005609:Free Radicals; D005978:Glutathione; D006735:Horseradish Peroxidase / Q000494:pharmacology*; D007097:Imines; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000494:pharmacology*; D011108:Polymers
chemical_list: D016227:Benzoquinones; D002250:Carbon Radioisotopes; D005609:Free Radicals; D007097:Imines; D011108:Polymers; D000082:Acetaminophen; C048043:N-acetyl-4-benzosemiquinone imine; D006735:Horseradish Peroxidase; D010544:Peroxidases; C028473:N-acetyl-4-benzoquinoneimine; D005978:Glutathione; C034780:3-(glutathion-S-yl)acetaminophen