Genetic Control of Tryptophan Peroxidase-Oxidase in Drosophila melanogaster

Abstract

BUTENANDT¹, Beadle² and Ephrussi³ have shown that kynurenine synthesis occurs in insects and that in D. melanogaster the gene ‘vermillion’ (ν) controls kynurenine formation. Tryptophan oxidation to kynurenine was extensively studied in mammal liver by Knox and Mehler⁴, who showed that two enzymes are involved in this two-step reaction: tryptophan peroxidase-oxidase and kynurenine formamidase. Since the mutant ν contains a normal amount of the latter enzyme⁵, it was thought that the first step of tryptophan oxidation, which leads to formylkynurenine, is in some way affected by this mutation. No direct demonstration of enzyme control by the ν gene has been given up to now; workers have tried unsuccessfully to demonstrate that tryptophan is metabolized in vitro by Drosophila extracts⁶. A very low content of tryptophan peroxidase-oxidase and the relative inadequacy of the methods of enzyme assay, account probably for these results. Only recently activity of tryptophan peroxidase-oxidase was recognized in an insect—the meal-moth Ephestia kuhniella ⁷, and quantitative determinations were made by measuring the fluorescence of chromatographically separated spots. This communication deals with the genetic control of tryptophan peroxidase oxidase in D. melanogaster studied by means of a very sensitive method.