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 c atalyzes the synthesis of adenosine 5'-tetraphosphate (p(4)A) and aden osine 5'-pentaphosphate (p(5)A) from ATP and tri-or tetrapolyphosphate , respectively, dATP, adenosine-5'-O-[gamma-thiotriphosphate] (ATP gam ma S), adenosine(5') tetraphospho(5')adenosine (Ap(4)A), and adenosine (5')pentaphospho(5')adenosine (Ap(5)A) are also substrates of the reac tion 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 A TP and P-3 are 0.015 and 1.3 mM, respectively, Maximum velocity was ob tained 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 a nd minimum activities were measured at pH values of 5.5 and 8.2, respe ctively; the opposite was observed for the synthesis of palmitoyl-CoA, with maximum activity in the alkaline range. The relative rates of sy nthesis of palmitoyl-CoA and p(4)A are around 10 (at pH 5.5) and aroun d 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 les ser extent, the enzyme catalyzes the synthesis also of Ap(4)A (from AT P), 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).