Effect of some tryptophan metabolites on the biosynthesis of pteridines in the mutant red malpighian tubules of Drosophila melanogaster

The mutation red Malpighian tubules (red) of Drosophila melanogaster present a strong interaction with some ommochrome-deficient mutations. This interaction consisted of a change in the pool levels of various pteridines and in the guanosine triphosphate cyclohydroase (GTPCH) activity of the eyes. The blockage of the synthesis of the tryptophan metabolite 3-hydroxykynurenine (HK) is responsible for this interaction. However, this blockage does not affect the pteridine pattern in the absence of the red mutation. The effect of HK has been deduced from the pteridine pattern and GTPCH activities of various double mutant strains and has been strengthened by the experiments of dietary supplementation with HK. This effect is not due to an inhibition of GTPCH activity by HK.