The isolation and identification of an intermediate involved in the biosynthesis of drosopterin in Drosophila melanogaster.

A compound that is involved in the biosynthesis of the drosopterin eye pigments has been isolated from the heads of Drosophila melanogaster. Analyses of this compound by chemical, mass spectral, and proton nuclear magnetic resonance techniques in conjunction with biochemical considerations provide evidence for the structure 2-amino-4-oxo-6-acetyl-7,8-dihydro-3H,9H-pyrimido[4,5-b][1,4]diazepine (PDA). At least three eye pigments (drosopterin, isodrosopterin, and aurodrosopterin) are synthesized when PDA and 2-amino-4-oxo-(D-erythro-1',2',3'-trihydroxypropyl)-7.8-dihydropteridine triphosphate (dihydroneopterin triphosphate) are incubated with Mg2+ and protein fractions prepared from Drosophila heads. The synthesis of aurodrosopterin, in addition, requires reduced pyridine nucleotide. Other evidence suggests that dihydroneopterin triphosphate is a biosynthetic precursor of PDA.