Biosynthesis of dihydroxanthommatin: In vitro enzymatic reduction of xanthommatin

A new enzyme was partially purified from Drosophila melanogaster. It has a molecular weight of about 55,000 and catalyzes the reduction of xanthommatin to dihydroxanthommatin in the presence of NADH/H + as cofactor. FAD, FMN, p- chloromercuribenzoate , 2-amino-4-hydroxypteridine and biopterin inhibited the enzyme activity. The nature of this inhibition was examined further. The inhibitory effect from the pterinic ring, especially from biopterin and 2-amino-4-hydroxypteridine, suggests a correlation between the synthesis of dihydroxanthommatin and that of the pterines. It is suggested that the enzyme may participate in the reduction of xanthommatin.