PRODUCTION OF MELANINS BY CERULOPLASMIN

It was shown that ceruloplasmin, apart from the known oxidative conver sion of dopamine into melanin, can also produce (DHI)-melanin from 5,6 -dihydroxyindole and THP-melanin from tetrahydropapaveroline. Cerulopl asmin acts as an oxidase and the kinetic parameters for these oxidativ e reactions are reported. Since these ceruloplasmin-catalyzed reaction s occur also at pH 7.4, they could have a significant physiological im pact. This ceruloplasmin-oxidasic activity is enhanced by copper ions and inhibited by chelators, such as ethylenediaminetetraacetic acid (E DTA) and desferoxamine (DEF). Some possible implication of melanin pro duction in blood are discussed.