Benzoate-coenzyme A ligase from Thauera aromatica: an enzyme acting in anaerobic and aerobic pathways.
In the denitrifying member of the beta-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 acyl-CoA intermediate by a single CoA ligase (AMP forming) that preferentially acted on benzoate. This benzoate-CoA 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. A deletion mutant not only was unable to grow anaerobically on benzoate or 2-aminobenzoate, but also aerobic growth on benzoate was affected. This suggests that benzoate induces a single benzoate-CoA ligase. The product of benzoate activation, benzoyl-CoA, then acts as inducer of separate anaerobic or aerobic pathways of benzoyl-CoA, depending on whether oxygen is lacking or present.
Schühle
Karola
K
Mikrobiologie, Institut für Biologie II, Universität Freiburg, Germany.
Gescher
Johannes
J
Feil
Ulrich
U
Paul
Michael
M
Jahn
Martina
M
Schägger
Hermann
H
Fuchs
Georg
G
D000332:Aerobiosis; D000693:Anaerobiosis; D001565:Benzoates / Q000378:metabolism; D003001:Cloning, Molecular; D003066:Coenzyme A Ligases / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D017422:Sequence Analysis, DNA; D020628:Thauera / Q000201:enzymology* / Q000254:growth & development*
D001565:Benzoates; D009566:Nitrates; C070685:2-aminobenzoate coenzyme A ligase; D003066:Coenzyme A Ligases; C055455:benzoate coenzyme A ligase