Terminal synthesis of xanthommatin in Drosophila melanogaster. II. Enzymatic formation of the phenoxazinone nucleus

Xanthommatin, the brown eye pigment of Drosophila melanogaster is a phenoxazinone compound formed by the bimolecular oxidative condensation of 3-hydroxykynurenine. Evidence is presented in this report for an enzyme system in drosophila which catalyzes the formation of the phenoxazinone chromophore of xanthommatin. This enzyme system, which is separable from the interfering activities of phenol oxidase and cytochrome oxidase, is relatively inactive in crude extracts but can be activated either by heat treatment or by passage through Sephadex G-50. The preliminary characterization of several properties of the enzyme-catalyzed reaction and their biological significance are discussed.Supported by USPHS grant GM12323 and by the Robert A. Welch Foundation, Houston, Texas.Postdoctoral Fellow supported by USPHS (1 FO2 GM44, 562-01) and the Rosalie B. Hite Memorial Fund.