title: The role of 2,4,5-trihydroxyphenylalanine in melanin biosynthesis.
abstract: Both 3,4-dihydroxyphenylalanine and 2,4,5-trihydroxyphenylalanine were oxidized with periodate and mushroom tyrosinase to determine whether the latter compound is an intermediate in melanin biosynthesis. Matrix analysis of the spectra obtained with a rapid scan spectrophotometer and comparison of the spectra of quinone intermediates with model quinones disclosed that, although 2,4,5-trihydroxyphenylalanine can be oxidized to 2-carboxy-2,3-dihydroindole-5,6-quinone (dopachrome), this oxidation proceeds through a stable intermediate, 5-(2-carboxy-2-aminoethyl)-2-hydroxy-1,4-benzoquinone, which does not appear in the oxidation of 3,4-dihydroxyphenylalanine to dopachrome. Thus, these studies are in agreement with the original postulate, that 4-(2-carboxy-2-aminoethyl)-1,2-benzoquinone and leukodopachrome are the intermediates in the major pathway for dopachrome synthesis.
mesh_terms: D001487:Basidiomycota / Q000201:enzymology; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D008543:Melanins / Q000096:biosynthesis*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010084:Oxidation-Reduction; D010504:Periodic Acid; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet
chemical_list: D008543:Melanins; D010504:Periodic Acid; C001388:6-hydroxydopa; D004295:Dihydroxyphenylalanine; D014442:Monophenol Monooxygenase