Affiliation:
1. Serviço de Quı́mica Fisiológica, Faculdade de Medicina, Universidade do Porto, Porto, Portugal1
2. Departamento de Bioquı́mica, Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Cientı́ficas, Facultad de Medicina, Universidad Autónoma de Madrid, 28029 Madrid, Spain,2and
Abstract
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).
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
31 articles.
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