L-alanine aminotransferase in the paragonial gland of Drosophila

Abstract

The specific activity of l-alanine aminotransferase in the paragonial gland of Drosophila nigromelanica declines rapidly from day 7 to 15 post adult emergence and thereafter remains at a constant low level. In both D. nigromelanica and D. melanogaster there is a 2 to 3 fold increase in the enzyme activity following copulation. Experiments performed by injecting actinomycin D and labeled uridine into the mated flies suggest that the stimulation by mating involves de novo synthesis. The partially purified l-alanine aminotransferase from whole flies of D. nigromelanica migrates as a single band on 5% polyacrylamide gels and has a molecular weight of approximately 120,000 daltons. There is a broad pH optimum from 7.0 to 8.5. The Michaelis constants were calculated to be 4.54 and 0.50 mM for l-alanine and α-ketoglutarate respectively. The properties of the enzyme from both Drosophila species are identical.