This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Aromatic Compounds Degradation → 2-Aminobenzoate Degradation|
Some taxa known to possess this pathway include : Geobacillus thermodenitrificans NG80-2
Four types of aromatic compounds degradation pathways are thought to occur in different types of bacteria:
Aerobic organisms take advantage of the availability of molecular oxygen, and use oxygenases that introduce hydroxyl groups and cleave the aromatic ring. These pathways usually lead to a few central intermediates such as catechol, protocatechuate, and gentisate (see anthranilate degradation I (aerobic)).
Facultative aerobes utilize two types of pathways, depending on the availability of oxygen. When oxygen is present, these organisms use the so-called "hybrid" type of aerobic metabolism for some aromatic compounds, including benzoate, anthranilate and phenylacetate. These pathways use coenzyme A to activate and form thioesters of the substrates, followed by an oxygenase/reductase step to dearomatize (but not cleave) the ring. Cleavage of the dearomatized ring does not require oxygen (see anthranilate degradation II (aerobic)). Under anaerobic conditions, facultative aerobes and phototrophs use a reductive aromatic metabolism. The aromatic compounds are activated by coenzyme A to an active intermediate that can be transformed to important central intermediate such as benzoyl-CoA. Reduction of the aromatic ring of benzoyl-CoA is catalyzed by benzoyl-CoA reductase and is driven by the hydrolysis of 2 ATP molecules (see anthranilate degradation III (anaerobic)).
Strict anaerobes utilize a completely different and not well characterized benzoyl-coenzyme A reductase that does not utilize ATP [Fuchs08].
About This Pathway
Geobacillus thermodenitrificans NG80-2 degrades L-tryptophan to acetyl-CoA via the intermediates anthranilate and 3-hydroxyanthranilate. While L-tryptophan degradation via 3-hydroxyanthranilate is well documented in eukaryotes (although via a different pathway, as documented in pathway L-tryptophan degradation III (eukaryotic)), this is an unusual route for bacteria [Liu10a].
The key enzyme of the pathway, which converts anthranilate to 3-hydroxyanthranilate, is anthranilate hydroxylase. The gene encoding the protein has been cloned, expressed in Escherichia coli and purified, and was shown to be an FAD-dependent hydroxylase. The GTNG_3160 gene that encodes the enzyme is found in a cluster that also contains two additional genes that encode a riboflavin kinase/FMN adenylyltransferase and an FAD reductase, which together provide FAD for the hydroxylase [Liu10a].
Liu10a: Liu X, Dong Y, Li X, Ren Y, Li Y, Wang W, Wang L, Feng L (2010). "Characterization of the anthranilate degradation pathway in Geobacillus thermodenitrificans NG80-2." Microbiology 156(Pt 2);589-95. PMID: 19942660
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