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 → Phenolic Compounds Degradation|
Some taxa known to possess this pathway include : Aromatoleum aromaticum EbN1
Expected Taxonomic Range: Bacteria
The denitrifying bacterium Aromatoleum aromaticum EbN1 can utilize 1-ethyl-4-hydroxybenzene under anoxic conditions. A degradation pathway similar to the ethylbenzene degradation pathway found in this bacterium (see ethylbenzene degradation (anaerobic)) has been suggested [Wohlbrand08].
The pathway starts with an initial hydroxylation of 1-ethyl-4-hydroxybenzene to S-1-(4-hydroxyphenyl)-ethanol, followed by dehydrogenation to 4-hydroxyacetophenone. These intermediates have been confirmed. The later steps in the pathway have not been verified biochemically, but are predicted to include carboxylation and thiolytic cleavage yielding 4-hydroxybenzoyl-CoA, which is channeled into the central anaerobic benzoyl-CoA pathway (see benzoyl-CoA degradation II (anaerobic)).
The enzymes involved in the pathway are believed to be encoded in a single large operon ( approximately 15 kb). Among them are a p-cresol methylhydroxylase-like protein (encoded by pchC and pchF), proposed to be a p-ethylphenol methylhydroxylase, two predicted alcohol dehydrogenases (encoded by chnA and ebA309), a biotin-dependent carboxylase (encoded by xccA, xccB and xccC), an acetoacetyl-CoA synthetase-like protein (acsA) and a thiolase (tioL).
None of these enzymes has been verified biochemically at the moment. However, expression of these proteins was shown to be upregulated in cells adapted to anaerobic growth with 1-ethyl-4-hydroxybenzene and 4-hydroxyacetophenone [Wohlbrand08].
Wohlbrand08: Wohlbrand L, Wilkes H, Halder T, Rabus R (2008). "Anaerobic degradation of p-ethylphenol by "Aromatoleum aromaticum" strain EbN1: pathway, regulation, and involved proteins." J Bacteriol 190(16);5699-709. PMID: 18539747
Brackmann93: Brackmann R, Fuchs G (1993). "Enzymes of anaerobic metabolism of phenolic compounds. 4-Hydroxybenzoyl-CoA reductase (dehydroxylating) from a denitrifying Pseudomonas species." Eur J Biochem 1993;213(1);563-71. PMID: 8477729
Gibson97: Gibson J, Dispensa M, Harwood CS (1997). "4-hydroxybenzoyl coenzyme A reductase (dehydroxylating) is required for anaerobic degradation of 4-hydroxybenzoate by Rhodopseudomonas palustris and shares features with molybdenum-containing hydroxylases." J Bacteriol 179(3);634-42. PMID: 9006014
Johannes08: Johannes J, Unciuleac MC, Friedrich T, Warkentin E, Ermler U, Boll M (2008). "Inhibitors of the molybdenum cofactor containing 4-hydroxybenzoyl-CoA reductase." Biochemistry 47(17);4964-72. PMID: 18393440
Park06: Park YJ, Yoo CB, Choi SY, Lee HB (2006). "Purifications and characterizations of a ferredoxin and its related 2-oxoacid:ferredoxin oxidoreductase from the hyperthermophilic archaeon, Sulfolobus solfataricus P1." J Biochem Mol Biol 39(1);46-54. PMID: 16466637
Rabus05: Rabus R, Kube M, Heider J, Beck A, Heitmann K, Widdel F, Reinhardt R (2005). "The genome sequence of an anaerobic aromatic-degrading denitrifying bacterium, strain EbN1." Arch Microbiol 183(1);27-36. PMID: 15551059
Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216
Wohlbrand07: Wohlbrand L, Kallerhoff B, Lange D, Hufnagel P, Thiermann J, Reinhardt R, Rabus R (2007). "Functional proteomic view of metabolic regulation in "Aromatoleum aromaticum" strain EbN1." Proteomics 7(13);2222-39. PMID: 17549795
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