title: Specific magnesium-dependent diadenosine 5',5'''-P1,P3-triphosphate pyrophosphohydrolase in Escherichia coli.
abstract: A specific Mg2+-dependent bis(5'-adenosyl)-triphosphatase (EC 3.6.1.29) was purified 270-fold from Escherichia coli. The enzyme had a strict requirement for Mg2+. Other divalent cations, such as Mn2+, Ca2+, or Co2+, were not effective. The products of the reaction with bis(5'-adenosyl) triphosphate (Ap3A) as the substrate were ADP and AMP in stoichiometric amounts. The Km for Ap3A was 12 +/- 5 microM. Bis(5'-adenosyl) di-, tetra-, and pentaphosphates, NAD+, ATP, ADP, AMP, glucose 6-phosphate, p-nitrophenylphosphate, bis-p-nitrophenylphospate, and deoxyribosylthymine-5'-(4-nitrophenylphosphate) were not substrates of the reaction. The enzyme had a molecular mass of 36 kilodaltons (as determined both by gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis), an isoelectric point of 4.84 +/- 0.05, and a pH optimum of 8.2 to 8.5. Zn2+, a known potent inhibitor of rat liver bis(5'-adenosyl)-triphosphatase and bis(5'-guanosyl)-tetraphosphatase (EC 3.6 1.17), was without effect. The enzyme differs from the E. coli diadenosine 5',5'''-P1, P4-tetraphosphate pyrophosphohydrolase which, in the presence of Mn2+, also hydrolyzes Ap3A.
mesh_terms: D017766:Acid Anhydride Hydrolases; D000227:Adenine Nucleotides / Q000378:metabolism; D015226:Dinucleoside Phosphates; D004926:Escherichia coli / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D010744:Phosphoric Monoester Hydrolases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D015032:Zinc / Q000494:pharmacology; D000099170:Bis(5'-adenosyl)triphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D000227:Adenine Nucleotides; D015226:Dinucleoside Phosphates; D008274:Magnesium; D010744:Phosphoric Monoester Hydrolases; D015032:Zinc; D000099170:Bis(5'-adenosyl)triphosphatase; C011440:diadenosine triphosphate