title: [Enzymes of the inosinic crossing point in human lymphocytes].
abstract: At the "inosinic branch point", inosinic acid (IMP) can be channelled either to guanylic acid (GMP) or to adenylic acid (AMP). The 4 enzymes involved in these processes are IMP-dehydrogenase (IMP-DH) and GMP synthetase for the formation of GMP and adenylosuccinate (AMP-S) synthetase and lyase for the formation of AMP. The Authors study the behavior of these enzymes in peripheral blood lymphocytes from normal and leukemic patients. The cells were isolated as previously reported. GMP synthetase was assayed with radiochemical method, IMP-DH and AMP-S synthetase with a radiochemical method coupled to HPLC, while AMP-S lyase was determined following the formation of AMP separated by AMP-S by HPLC, without using labelled precursors. Except for GMP synthetase, which was very low, no activity was detectable in normal lymphocytes; while AMP-S was absent also in leukemic cells, the remaining three activities were well evident. The results open the possibility of using the inosinic branch point enzymes as tumor markers.
authors.affiliation: Istituto di Chimica Biologica, Università di Siena.
authors.forename: A
authors.initials: A
authors.lastname: Tabucchi
authors.forename: D
authors.initials: D
authors.lastname: Vannoni
authors.forename: B
authors.initials: B
authors.lastname: Porcelli
authors.forename: A
authors.initials: A
authors.lastname: Di Stefano
authors.forename: M
authors.initials: M
authors.lastname: Pizzichini
authors.forename: R
authors.initials: R
authors.lastname: Leoncini
authors.forename: E
authors.initials: E
authors.lastname: Dispensa
authors.forename: E
authors.initials: E
authors.lastname: Marinello
mesh_terms: D000264:Adenylosuccinate Lyase / Q000378:metabolism; D000265:Adenylosuccinate Synthase / Q000378:metabolism; D019731:Carbon-Nitrogen Ligases; D006801:Humans; D007168:IMP Dehydrogenase / Q000378:metabolism; D007291:Inosine Monophosphate / Q000378:metabolism*; D007292:Inosine Nucleotides / Q000378:metabolism*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000201:enzymology*; D008025:Ligases / Q000378:metabolism; D008214:Lymphocytes / Q000201:enzymology*
chemical_list: D007292:Inosine Nucleotides; D007291:Inosine Monophosphate; D007168:IMP Dehydrogenase; D000264:Adenylosuccinate Lyase; D008025:Ligases; D019731:Carbon-Nitrogen Ligases; D000265:Adenylosuccinate Synthase; C020828:GMP synthase (glutamine-hydrolyzing)