Abstract
Ten eye-color mutants (ge and its allele ge2, ocra and its allele ocrac, w57, do, car, cm, rb and bu) of the housefly, Musca domestica L., were studied for tryptophan metabolism.
1) A great amount of accumulation of tryptophan was observed in pupae of the ge mutant, while neither kynurenine nor 3 OH-kynurenine were detected. No xanthommatin exists in eyes of adults of this mutant. Therefore, ge is a mutant blocked at the first step of tryptophan metabolism. It was proved that ge and ge2 have no activity of tryptophan pyrrolase in cell-free extracts.
2) In pupae of ocra and ocrac mutants, an excessive amount of kynurenine was accumulated, but 3 OH-kynurenine was undetectable. Thus, these are mutants whose activities of kynurenine hydroxylase are genetically blocked. Xanthommatin was undetected in eyes of adults of ocra. In ocrac, however, it was proved that a little amount of the pigment was accumulated (8 to 10% of the wild type). The ocrac may be a leaky mutant of kynurenine hydroxylase.
3) In do (dark-orange), tryptophan accumulated in 5 times the amount of that in the wild-type pupae, while accumulations of kynurenine and 3 OH-kynurenine were normally observed. Enzymatic activity of over-all conversion from tryptophan to kynurenine in the cell-free extract of this mutant was half of the wild-type.
4) It is likely that ge and ocra mutants of the housefly are homologous to the v and cn mutants of D. melanogaster, respectively.
5) Separation of tryptophan pyrrolase from kynurenine formamidase was obtained by gradient elution chromatography on a DEAF-column.
