title: Tyrosinase-mediated oxidation of acetaminophen to 4-acetamido-o-benzoquinone.
abstract: Based on its monophenolic structure and given its pharmacological and toxicological importance, the ability of tyrosinase to oxidize acetaminophen was studied for the first time. Progress curves showed a transient phase characteristic of the monophenolase activity of tyrosinase prior to attaining the steady-state. The duration of this transient phase strongly increased with the drug concentration, which would partly explain why paracetamol oxidation by tyrosinase has not been studied hitherto. The pathway is enhanced by the presence of minute amounts of L-dopa, which shortens the length of the lag period. Acetaminophen oxidation was inhibited by tropolone, a selective inhibitor of tyrosinase. The presence of the corresponding o-diphenol as intermediate was demonstrated with ascorbic acid by chemical oxidation using NaIO4 and by HPLC analysis, indicating that acetaminophen is oxidized by the monophenolase activity of tyrosinase to its corresponding o-quinone. These results contribute to our knowledge of the oxidation mechanisms of acetaminophen.
authors.affiliation: Departamento de Química-Fisica, Escuela Politécnica Superior de Albacete, Universidad de Castilla-La Mancha, Campus Universitario, E-02071 Albacete, Spain.
authors.forename: Edelmira
authors.initials: E
authors.lastname: Valero
authors.forename: Ramón
authors.initials: R
authors.lastname: Varón
authors.forename: Francisco
authors.initials: F
authors.lastname: García-Carmona
mesh_terms: D000082:Acetaminophen / Q000378:metabolism*; D000363:Agaricales / Q000201:enzymology; D018712:Analgesics, Non-Narcotic / Q000378:metabolism*; D016227:Benzoquinones / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D007980:Levodopa / Q000494:pharmacology; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000187:drug effects; D011048:Polarography; D013056:Spectrophotometry, Ultraviolet
chemical_list: D018712:Analgesics, Non-Narcotic; D016227:Benzoquinones; D000082:Acetaminophen; D007980:Levodopa; C046225:2-acetamido-4-benzoquinone; D014442:Monophenol Monooxygenase