title: Diadenosine 5",5"'P1,P4-tetraphosphatase in Drosophila embryos: developmental regulation and characterization.
abstract: 1. An enzyme has been isolated from Drosophila embryos which specifically hydrolyzes dinucleoside tetraphosphates to the corresponding nucleoside tri- and tetraphosphates, with Km values around 4 microM. 2. Nucleoside mono-, di- and triphosphates are competitive inhibitors with K1 values i the 0.01 mM range. 3. The inhibition is particularly strong by adenosine tetraphosphate (Ki = 10 nM). 4. The enzyme is maximally active at pH 7.5 and is quite stable at acid pH. 5. The enzyme requires divalent cations for activity: Co(2+) much greater than [corrected] Mn(2+) Mg(2+) x Co(2+) stimulated about 90-fold at 6 mM. 6. The specific stimulation by Co(2+) has been described before, but at lower concentrations, for the enzyme of procaryotes which splits diadenosine tetraphosphate symmetrically. Zn(2+) and Ca(2+) are inhibitors of the Drosophila enzyme. Co(2+) is also inhibitor in the presence of Mg(2+). 7. The Drosophila enzyme has essential sulphydryl group(s) and a molecular weight of 26,000. 8. Diadenosine tetraphosphatase is present in mature oocytes and increases after fertilization to reach a peak 1.5 hr later. 9. From this time to 3.5 hr the activity decreased to remain at a plateau until the end of embryogenesis. 10. The profile of activity is compatible with its involvement in the regulation of nuclear division.
authors.affiliation: Instituto de Investigaciones Biomédicas, C.S.I.C., Facultad de Medicina, Madrid, España.
authors.forename: C G
authors.initials: CG
authors.lastname: Vallejo
authors.forename: P
authors.initials: P
authors.lastname: Leon
mesh_terms: D017766:Acid Anhydride Hydrolases; D000227:Adenine Nucleotides / Q000378:metabolism; D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D004331:Drosophila melanogaster / Q000196:embryology / Q000201:enzymology*; D006159:Guanosine Tetraphosphate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D009865:Oocytes / Q000201:enzymology; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D013379:Substrate Specificity; D013439:Sulfhydryl Reagents / Q000494:pharmacology
chemical_list: D000227:Adenine Nucleotides; D002413:Cations, Divalent; D013439:Sulfhydryl Reagents; D006159:Guanosine Tetraphosphate; D010727:Phosphoric Diester Hydrolases; D017766:Acid Anhydride Hydrolases; C036849:bis(5'-nucleosyl)tetraphosphatase (symmetrical)