title: Identification by electron spin resonance of free radicals formed during the oxidation of 4-hydroxyanisole catalyzed by tyrosinase.
abstract: We have observed the formation of free radicals during the oxidation of the melanocytotoxic agent 4-hydroxyanisole with the enzyme tyrosinase as a catalyst. The first free radical to form is identified as the 4-methoxy-1,2-benzosemiquinone radical anion. The peak concentration of this radical increases with tyrosinase concentration; a minimum concentration of 50 micrograms/ml of tyrosinase was needed to observe this radical. The peak concentration of this radical is independent of 4-hydroxyanisole concentration. This radical is produced by reverse dismutation of the primary product, 4-methoxy-1,2-benzoquinone and 4-methoxycatechol produced indirectly.
mesh_terms: D000840:Anisoles / Q000378:metabolism*; D001487:Basidiomycota / Q000201:enzymology; D004156:Catechol Oxidase / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D006735:Horseradish Peroxidase; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D010944:Plants / Q000201:enzymology
chemical_list: D000840:Anisoles; D005609:Free Radicals; C009760:mequinol; D004156:Catechol Oxidase; D006735:Horseradish Peroxidase; D014442:Monophenol Monooxygenase