Melanin from several insect samples was isolated and subjected to chemical degradation and HPLC analysis for melanin markers. Quantification of different melanin markers reveals that insect melanins are significantly different from that of the mammalian epidermal melanins. The eumelanin produced in mammals is derived from the oxidative polymerization of both 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acids. The pheomelanin is formed by the oxidative polymerization of cysteinyldopa. Thus, dopa is the major precursor for both eumelanin and pheomelanin in mammals. But insect eumelanin appears to be mostly made from 5,6-dihydroxyindole and originates from dopamine. More importantly, our study points out the wide spread occurrence of pheomelanin in many insect species. In addition, cysteinyldopamine and not cysteinyldopa is the major precursor for insect pheomelanin. Thus, both eumelanin and pheomelanin in insects differ from higher animals using dopamine and not dopa as the major precursor.
Keywords: cysteinyldopa; cysteinyldopamine; dihydroxyindole melanin; dihydroxyindole-2-carboxylic acid melanin; dopa melanin; dopachrome decarboxylase/tautomerase; dopachrome tautomerase; dopamine melanin; insect melanogenesis.
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