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

Acyl coenzyme A (CoA) synthetase (EC 6.2.1.8) from Pseudomonas fragi catalyzes the synthesis of adenosine 5'-tetraphosphate (p4A) and adenosine 5'-pentaphosphate (p5A) from ATP and tri- or tetrapolyphosphate, respectively. dATP, adenosine-5'-O-[gamma-thiotriphosphate] (ATP gamma S), adenosine(5')tetraphospho(5')adenosine (Ap4A), and adenosine(5')pentaphospho(5')adenosine (Ap5A) are also substrates of the reaction yielding p4(d)A in the presence of tripolyphosphate (P3). UTP, CTP, and AMP are not substrates of the reaction. The K(m) values for ATP and P3 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 P3. The relative rates of synthesis of p4A with divalent cations were Mg = Co > Mn = Zn >> Ca. In the pH 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 p4A are around 10 (at pH 5.5) and around 200 (at pH 8.2). The synthesis of p4A 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 Ap4A (from ATP), Ap5A (from p4A), and adenosine(5')tetraphospho(5')nucleoside (Ap4N) from adequate adenylyl donors (ATP, ATP gamma S, or octanoyl-AMP) and adequate adenylyl acceptors (nucleoside triphosphates).