ENZYMATIC STUDIES ON THE HYDROXYLATION OF KYNURENINE IN DROSOPHILA MELANOGASTER

Abstract

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(BAGLIONI , 1960KAUFMAN 1962; MARZ-LUF 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. MATERIALS A N D METHODSWild type Oregon-R and the white mutant of Drosophila melanogaster were from stocks malntained in our laboratories. The cinnabar mutant was obtained from the California Institute of Technology. Flies were raised at a temperature of 23" in large populations accordhg to the method of MITCHELL and MITCHELL (1964). Eggs were collected over 4 to 5 hours in plastic bread boxes spread with standard cornmeal agar medium. Samples of larvae and pupae, at different stages of development, were harvested for experiments following the method of MITCHELL and MITCHELL. Preparation. partial purd;fication and assay of kynurenine hydroxylase in wild-type. (A) Crude homogenate:To each gram of chilled material (larvae, pupae or adults) were added 1.4 amoles NADPH?. 2 0 units glucose-6-phosphate dehydrogenase (Sigma) (KORNBERG 1950), 130 amoles glucose-6-phosphate, 1.2 pmoles potassium cyanide, and 260 pmoles phosphate buffer (pH 7.5). Total volume of fluid added was 1.4 ml. A glass-Teflon tissue grinder fitted into a mechanical

Effect of Tryptophan Metabolites on Fluorescent Granules in the Malpighian Tubules of Eye Color Mutants of Drosophila melanogaster

“…The wild type alleles of v, cn, st, ltd and w encode products that are required for the brown pigmentation. Two of them, v and cn are nonautonomous mutants and encode the enzymes tryptophan oxygenase (Baglioni, 1959(Baglioni, , 1960Kaufman, 1962;Baillie and Chovinick, 1971) and kynurenine-3-hydroxylase (Ghosh and Forrest, 1967;Sullivan et al, 1973), respectively. The roles of the autonomous mutant genes st, ltd and whave not been clarified.…”

Modulating the Kynurenine pathway or sequestering toxic 3-hydroxykynurenine protects the retina from light-induced damage in Drosophila

“…This led to the suggestion that loss of st leads to accumulation of 3OH-K outside the LRO [26,41]. In line with this, we hypothesized that excess cytoplasmic 3OH-K levels are responsible for the enhancing effects on the w ndelT retinal phenotype upon removal of one copy of st. To test this hypothesis, we utilized mutations in cinnabar (cn), the gene that encodes kynurenine monooxygenase (KMO), an enzyme that catalyzes the formation of 3OH-K from Kynurenine [46][47][48] (Fig 1A). We expected that reduced levels of 3OH-K by lowering or removing cn activity should attenuate the detrimental effects exerted by loss of st on the w ndelT phenotype.…”

Modulating the Kynurenine pathway or sequestering toxic 3-hydroxykynurenine protects the retina from light induced damage in Drosophila

“…This led to the suggestion that loss of st leads to accumulation of 3OH-K outside the LRO (Cunningham et al, 2018, Mackenzie et al, 2000. In line with this, we hypothesized that excess cytoplasmic 3OH-K levels are responsible for the enhancing effects on the w ndelT retinal phenotype upon removal of one copy of st. To test this hypothesis, we utilized mutations in cinnabar (cn), the gene that encodes kynurenine monooxygenase (KMO), an enzyme that catalyzes the formation of 3OH-K from Kynurenine (Ghosh & Forrest, 1967, Sullivan, Kitos et al, 1973, Warren, Palmer et al, 1996 (Fig. 1A).…”