Enzymatic studies on the hydroxylation of kynurenine in Drosophila melanogaster.

HE classic pathway for brown pigment synthesis in Drosophila melanogaster, as determined by the accumulation of intermediates, involves the sequence, tryptophan -+ formyl kynurenine + kynurenine -+ 3-hydroxykynurenine -+ brown pigments (for review see ZIEGLER 1961). Two of the enzymes in this pathway. tryptophan pyrrolase (BAGLIONI 1959, 1960; KAUFMAN 1962; MARZLUF 1965a, b) and kynurenine formamidase (GLASSMAN 1956) have been described. and the absence of tryptophan pyrrolase in the vermilion mutant of Drosophila has been documented. However. the enzyme catalyzing the conversion of kynurenine into hydroxykynurenine has never been described in Drosophila, although it has been shown to be present in a mammalian system (DE CASTRO, PRICE and BROWN 1956), and some of its characteristics, as studied in this system, are known (SAITO, HAYAISHI. and ROTHBERG 1957). In this paper the existence of this enzyme in Drosophila, its virtual absence in the mutant cinnabar, and its very greatly reduced activity in the mutant white, are demonstrated. On the other hand, tryptophan pyrrolase activity in extracts of the cinnabar and white mutants is the samc as in extracts ,of wild type.