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Radical Production During Tyrosinase Reaction, Dopa-Melanin Formation, and Photoirradiation of Dopa-Melanin

1984; Elsevier BV; Volume: 82; Issue: 6 Linguagem: Inglês

10.1111/1523-1747.ep12261311

1523-1747

Yasushi Tomita, Akiko Hariu, Chikako Kato, Makoto Seiji,

Plant Gene Expression Analysis

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.