Yeast diadenosine 5',5'''-P1,P4-tetraphosphate alpha,beta-phosphorylase behaves as a dinucleoside tetraphosphate synthetase.
The diadenosine 5',5'''-P1,P4-tetraphosphate alpha,beta-phosphorylase (Ap4A phosphorylase), recently observed in yeast [Guaranowski, A., & Blanquet, S. (1985) J. Biol. Chem. 260, 3542-3547], is shown to be capable of catalyzing the synthesis of Ap4A from ATP + ADP, i.e., the reverse reaction of the phosphorolysis of Ap4A. The synthesis of Ap4A markedly depends on the presence of a divalent cation (Ca2+, Mn2+, or Mg2+). In vitro, the equilibrium constant K = ([Ap4A][Pi])/[(ATP][ADP]) is very sensitive to pH. Ap4A synthesis is favored at low pH, in agreement with the consumption of one to two protons when ATP + ADP are converted into Ap4A and phosphate. Optimal activity is found at pH 5.9. At pH 7.0 and in the presence of Ca2+, the Vm for Ap4A synthesis is 7.4 s-1 (37 degrees C). Ap4A phosphorylase is, therefore, a valuable candidate for the production of Ap4A in vivo. Ap4A phosphorylase is also capable of producing various Np4N' molecules from NTP and N'DP. The NTP site is specific for purine ribonucleotides (N = A, G), whereas the N'DP site has a broader specificity (N' = A, C, G, U, dA). This finding suggests that the Gp4N' nucleotides, as well as the Ap4N' ones, could occur in yeast cells.
Brevet
A
A
Laboratoire de Biochimie, Unité Associée 240 du Centre National de la Recherche Scientifique, Palaiseau, France.
Coste
H
H
Fromant
M
M
Plateau
P
P
Blanquet
S
S
D017766:Acid Anhydride Hydrolases; D000227:Adenine Nucleotides / Q000096:biosynthesis*; D002413:Cations, Divalent; D015226:Dinucleoside Phosphates; D004492:Edetic Acid / Q000494:pharmacology; D007700:Kinetics; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D012265:Ribonucleotides / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D013379:Substrate Specificity
D000227:Adenine Nucleotides; D002413:Cations, Divalent; D015226:Dinucleoside Phosphates; D012265:Ribonucleotides; C020733:diadenosine tetraphosphate; D004492:Edetic Acid; D010727:Phosphoric Diester Hydrolases; D017766:Acid Anhydride Hydrolases; C036849:bis(5'-nucleosyl)tetraphosphatase (symmetrical)