Acyl coenzyme A synthetase from Pseudomonas fragi catalyzes the synthesis of adenosine 5′-polyphosphates and dinucleoside polyphosphates

Acyl coenzyme A (CoA) synthetase (EC 6.2.1.8) from Pseudomonas fragi catalyzes the synthesis of adenosine 5'-tetraphosphate (p(4)A) and adenosine 5'-pentaphosphate (p(5)A) from ATP and tri-or tetrapolyphosphate, respectively, dATP, adenosine-5'-O-[gamma-thiotriphosphate] (ATP gamma S), adenosine(5') tetraphospho(5')adenosine (Ap(4)A), and adenosine(5')pentaphospho(5')adenosine (Ap(5)A) are also substrates of the reaction yielding p(4)(d)A in the presence of tripolyphosphate (P-3). UTP, CTP, and AMP are not substrates of the reaction. The K-m values for ATP and P-3 are 0.015 and 1.3 mM, respectively, Maximum velocity was obtained in the presence of MgCl2, or CoCl2, equimolecular with the sum of ATP and P-3. The relative rates of synthesis of p(4)A with divalent cations were Mg = Co > Mn = Zn >> Ca. In the DH range used, maximum and minimum activities were measured at pH values of 5.5 and 8.2, respectively; the opposite was observed for the synthesis of palmitoyl-CoA, with maximum activity in the alkaline range. The relative rates of synthesis of palmitoyl-CoA and p(4)A are around 10 (at pH 5.5) and around 200 (ak pH 8.2). The synthesis of p(4)A is inhibited by CoA, and the inhibitory effect of CoA can be counteracted by fatty acids, To a lesser extent, the enzyme catalyzes the synthesis also of Ap(4)A (from ATP), Ap(5)A (from p,A), and adenosine(5')tetraphospho(5')nucleoside (Ap(4)N) from adequate adenylyl donors (ATP, ATP gamma S, or octanoyl-AMP) and adequate adenylyl accepters (nucleoside triphosphates).