Drosophila Arginase Is Produced from a Nonvital Gene That Contains the elav Locus within Its Third Intron

A Drosophila gene encoding a 351-amino acid-long predicted arginase (40% identity with vertebrate arginases) is reported. Interestingly, the third intron of thearginase gene includes the elav locus, whose coding sequence is on the complementary DNA strand to that of thearginase. Terrestrial vertebrates produce two arginases from duplicated genes. One form, essentially present in the liver, is a key enzyme of the urea cycle and eliminates excess ammonia through the excretion of urea. The function of the extrahepatic arginase, more ubiquitous, is not well understood. In macrophages, arginase competes with nitric-oxide synthase, which converts arginine into nitric oxide. Most organisms, including insects, produce only one type of arginase, whose function is not centered on ammonia detoxification. ADrosophila cDNA encoding a predicted arginase was isolated. It produces a 1.3-kilobase transcript present with highest levels toward the end of embryogenesis and thereafter. During embryogenesis, the arginase transcripts localize to the fat body. The first mutant allele of the Drosophila arginasegene was identified. It is predicted to produce a 199-amino acid-long C-terminally truncated protein, likely to be inactive. Preliminary characterization of the mutation shows that this recessive allele causes a developmental delay but does not affect viability.