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Acyl Coenzyme A Synthetase from Pseudomonas fragi Catalyzes the Synthesis of Adenosine 5′-Polyphosphates and Dinucleoside Polyphosphates

1998; American Society for Microbiology; Volume: 180; Issue: 12 Linguagem: Inglês

10.1128/jb.180.12.3152-3158.1998

1098-5530

Rui Fontes, Marı́a A. Günther Sillero, Antonio Sillero,

Biochemical and Molecular Research

ABSTRACT 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 -[γ-thiotriphosphate] (ATPγS), 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 MgCl 2 or CoCl 2 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 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 p 4 A are around 10 (at pH 5.5) and around 200 (at 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 4 A), and adenosine(5′)tetraphospho(5′)nucleoside (Ap 4 N) from adequate adenylyl donors (ATP, ATPγS, or octanoyl-AMP) and adequate adenylyl acceptors (nucleoside triphosphates).