CLONING OF AN ARYLALKYLAMINE N-ACETYLTRANSFERASE (AANAT1) FROM DROSOPHILA-MELANOGASTER EXPRESSED IN THE NERVOUS-SYSTEM AND THE GUT

In insects, neurotransmitter catabolism, melatonin precursor formation , and sclerotization involve arylalkylamine N-acetyltransferase (aaNAT , EC 2.3.1.87) activity, It is not known if one or multiple aaNAT enzy mes are responsible for these activities. We recently have purified an aaNAT from Drosophila melanogaster, Here, we report the cloning of th e corresponding aaNAT cDNA (aaNAT1) that upon COS cell expression acet ylates dopamine, tryptamine, and the immediate melatonin precursor ser otonin. aaNAT1 represents a novel gene family unrelated to known acety ltransferases, except in two weakly conserved amino acid motifs. In si tu hybridization studies of aaNAT1 mRNA in embryos reveal hybridizatio n signals in the brain, the ventral cord, the gut, and probably in oen ocytes, indicating a broad tissue distribution of aaNAT1 transcripts, Moreover, in day/night studies we demonstrate a diurnal rhythm of mela tonin concentration without a clear-cut change in aaNAT1 mRNA levels. The data suggest that tissue-specific regulation of aaNAT1 may be asso ciated with different enzymatic functions and do not exclude the possi bility of additional aaNAT genes.