title: Regulation of purine biosynthesis in cultured Drosophila melanogaster cells: II/relationships between hypoxanthine-guanine-phosphoribosyl transferase and 5'-nucleotidase.
abstract: All in vitro cell lines from Drosophila melanogaster do not possess measurable hypoxanthine - guanine - phosphoribosyltransferase (HGPRT) and 5'-nucleotidase activities. Nevertheless these enzymatic activities could be detected by the modification of culture conditions or treatment of crude extracts from Drosophila cells (1). A Drosophila melanogaster hemocyte line enabled demonstration of a relationship between the activities of HGPRT and 5'-nucleotidase. Only the addition of azaserine to the culture medium allows detection of a measurable amount of HGPRT and 5'-nucleotidase in cells devoid of endogenous synthesis of purine nucleotides. This action of azaserine suggests that the simultaneous expression of both enzymes is first directed by the suppression of the 5'-nucleotidase inhibition by pyrimidine nucleotides, and later on by the 5'-nucleotidase activity hydrolyzing the mononucleotides which inhibited the HGPRT, resulting its expression. This regulation system is confirmed by the simultaneous recovery of HGPRT and 5'-nucleotidase activities after heating cell cultures or cell extracts. Under such experimental conditions, 5'-nucleotidase is desensitized towards its negative effectors, while HGPRT regulation remains unchanged.
mesh_terms: D015720:5'-Nucleotidase; D000818:Animals; D001377:Azaserine / Q000494:pharmacology; D001773:Blood Cells / Q000201:enzymology*; D002460:Cell Line; D004331:Drosophila melanogaster; D006434:Hemocytes / Q000187:drug effects / Q000201:enzymology*; D006358:Hot Temperature; D007041:Hypoxanthine Phosphoribosyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009708:Nucleotidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010754:Phosphoribosyl Pyrophosphate / Q000378:metabolism
chemical_list: D010754:Phosphoribosyl Pyrophosphate; D001377:Azaserine; D007041:Hypoxanthine Phosphoribosyltransferase; D009708:Nucleotidases; D015720:5'-Nucleotidase