title: Radical production during tyrosinase reaction, dopa-melanin formation, and photoirradiation of dopa-melanin.
abstract: It has been suggested that superoxide anion (O2-) may be produced during eumelanin formation and during the photoirradiation of eumelanin , but no direct evidence for this has yet been reported (although O2- production during photoirradiation of pheomelanin has been shown). In this report, the production of O2- was investigated during the formation and photoirradiation of dopa-melanin, a synthetic eumelanin . It was found that cytochrome c was reduced during the tyrosinase reaction and dopa-melanin formation in vitro; this reduction could not be inhibited by superoxide dismutase (SOD). When dopa-melanin was irradiated by UV radiation or by visible light, high nitroblue tetrazolium (NBT) reduction was observed; this reduction was proportional to the light energy and the amount of dopa-melanin. NBT reduction by visible light could be slightly inhibited by SOD, but a 12% decrease of NBT reduction by UV radiation could be shown with the addition of SOD. These observations indicate that some radicals were produced during the tyrosinase reaction and dopa-melanin formation. Further, when dopa-melanin was irradiated, radicals were also produced, some of which were thought to consist of O2-, but others were unknown.
mesh_terms: D004156:Catechol Oxidase / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000528:radiation effects; D008027:Light; D008544:Melanocytes / Q000201:enzymology*; D014442:Monophenol Monooxygenase / Q000378:metabolism; D010084:Oxidation-Reduction; D013481:Superoxides; D014466:Ultraviolet Rays
chemical_list: D003574:Cytochrome c Group; D013481:Superoxides; D004295:Dihydroxyphenylalanine; C040616:DOPA melanin; D004156:Catechol Oxidase; D014442:Monophenol Monooxygenase