title: Chemical and enzymatic oxidation of 4-methylcatechol in the presence and absence of L-serine. Spectrophotometric determination of intermediates.
abstract: A pathway for 4-methylcatechol oxidation by tyrosinase (monophenol, dihydroxy-L-phenylalanine:oxygen oxidoreductase, EC 1.14.18.1) in the presence of L-serine is proposed. Characterization of intermediates in this oxidative reaction and stoichiometry determination have both been performed. It has been possible to detect spectrophotometrically 4-methyl-o-benzoquinone as the first intermediate in this pathway after oxidizing 4-methylcatechol with epidermis tyrosinase or sodium periodate at pH 6.5. The steps for 4-methylcatechol transformation in the presence of L-serine could be: 4-methylcatechol----4-methyl-o-benzoquinone----5-methyl-4N-serine-catechol----5 - methyl-4N-serine-o-benzoquinone. Matrix analysis of the spectra obtained with a rapid-scan spectrophotometer verified that 4-methyl-o-benzoquinone was transformed into 5-methyl-4N-serine-o-benzoquinone at a constant ratio, the stoichiometry for this conversion being the equation: 2-(4-methyl-o-benzoquinone) + L-serine----4-methylcatechol + 5-methyl-4N-serine-o-benzoquinone.
mesh_terms: D000818:Animals; D004156:Catechol Oxidase / Q000378:metabolism*; D002396:Catechols / Q000378:metabolism; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010084:Oxidation-Reduction; D011485:Protein Binding; D011893:Rana esculenta; D012694:Serine / Q000494:pharmacology*; D012867:Skin / Q000201:enzymology; D013053:Spectrophotometry
chemical_list: D002396:Catechols; C018599:4-methylcatechol; D012694:Serine; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase