Benzoate-Coenzyme A Ligase from Thauera aromatica : an Enzyme Acting in Anaerobic and Aerobic Pathways

Abstract

In the denitrifying member of the ␤-Proteobacteria Thauera aromatica, the anaerobic metabolism of aromatic acids such as benzoate or 2-aminobenzoate is initiated by the formation of the coenzyme A (CoA) thioester, benzoyl-CoA and 2-aminobenzoyl-CoA, respectively. Both aromatic substrates were transformed to the acylCoA intermediate by a single CoA ligase (AMP forming) that preferentially acted on benzoate. This benzoateCoA ligase was purified and characterized as a 57-kDa monomeric protein. Based on V max /K m, the specificity constant for 2-aminobenzoate was 15 times lower than that for benzoate; this may be the reason for the slower growth on 2-aminobenzoate. The benzoate-CoA ligase gene was cloned and sequenced and was found not to be part of the gene cluster encoding the general benzoyl-CoA pathway of anaerobic aromatic metabolism. Rather, it was located in a cluster of genes coding for a novel aerobic benzoate oxidation pathway. In line with this finding, the same CoA ligase was induced during aerobic growth with benzoate.

Anaerobic and aerobic cleavage of the steroid core ring structure by Steroidobacter denitrificans

“…This hypothesis is supported by the wide distribution of 16S rRNA gene sequences of S. denitrifi cans strains in oxic and anoxic environments. Similar (but not as extreme) cases were reported in the literature for a number of facultative anaerobes, such as Thauera aromatica ( 36 ) and Azoar cus evansii ( 37 ). These bacteria can use benzoate and phenylacetate under oxic and anoxic conditions ( 34,(36)(37)(38).…”

Bacterial Degradation of Benzoate

“…Thauera and Magnetospirillum strains, that degrade benzoate both aerobically via the box pathway and anaerobically via the bzd pathway share the same benzoateCoA ligase (bclA gene) for both pathways, and they have a single boxR gene associated to the box cluster in their genomes (22,66). On the contrary, Azoarcus sp.…”

“…1B). Although the box pathway becomes a major route for aerobic benzoate degradation and its biochemistry and genetics have been investigated in some bacteria, thus far there is no information about the regulatory mechanism that controls the inducible expression of the box genes (14,22,24). Interestingly, a common feature of most box clusters is the presence of a boxR gene, first described in Azoarcus strains (14,25), that encodes a protein that might be a member of the BzdR subfamily of prokaryotic transcriptional regulators (26,27) and, therefore, might constitute the regulatory unit of the box cluster (Fig.…”

“…The 3,4-dehydroadipyl-CoA semialdehyde formed becomes converted to succinyl-CoA and acetyl-CoA by a ␤-oxidation-like metabolism (box lower pathway) (Fig. 1A) (8,(13)(14)(15)(16)(17)(18)(19)(20)(21)(22).…”

Anaerobic Metabolism of Catechol by the Denitrifying Bacterium Thauera aromatica —a Result of Promiscuous Enzymes and Regulators?

“…For the specific activities of the purified 3-hydroxybenzoate-and 4-hydroxybenzoate-CoA ligases, see the text. The benzoate-CoA ligase activities were as follows (33): with benzoate, 16.5 mol min Ϫ1 mg Ϫ1 ; with 3-hydroxybenzoate, Ͻ1 mol min Ϫ1 mg Ϫ1 ; with 4-hydroxybenzoate, Ͻ1 mol min Ϫ1 mg Ϫ1 ; and with protocatechuate, Ͻ1 mol min Ϫ1 mg Ϫ1 .…”