Ethylbenzene often enters the environment as a result of petroleum-based industrial discharges or spills; it can be a component of the "mixed xylene" solutions contained therein. The compound is also used in the manufacturing of styrene and synthetic polymers. The anaerobic degradation of ethylbenzene is documented elsewhere in the EAWAG-BBD, and here the aerobic catabolism proceeds via two primary pathways. Pseudomonas sp. strain NCIB 10643 has been shown to utilize a wide range of n-alkylbenzenes (C2-C7), of which ethylbenzene is a single example. This degradation is initiated by a dioxygenation of the aromatic ring, leading to an extradiol ring cleavage.
It is reported by Lee & Gibson (1996) that napthalene dioxygenase exhibits a highly relaxed substrate specificity and is capable of aerobically degrading ethylbenzene to styrene and/or 2-hydroxyacetophenone. Information concerning the further degradation of 2-hydroxyacetophenone is not available, though 4-hydroxyacetophenone can undergo aerobic biodegradation. Naphthalene dioxygenase has many other catalytic abilities, which are documented in a table of the Reactions of Naphthalene 1,2-Dioxygenase.
The following is a text-format ethylbenzene pathway map. Organisms which can initiate the pathway are given, but other organisms may also carry out later steps. Follow the links for more information on compounds or reactions. This map is also available in Graphic (21k) format.
Ethylbenzene Ethylbenzene Ethylbenzene Pseudomonas putida 39/D Pseudomonas sp. Pseudomonas sp. Pseudomonas sp. NCIB 10643 NCIB 9816-4 NCIB 9816-4 | | | | | | | ethylbenzene | naphthalene | naphthalene | dioxygenase | 1,2-dioxygenase | 1,2-dioxygenase | | | v v v cis-2,3-Dihydroxy- Styrene (S)-1-Phenethyl 2,3-dihydro- | alcohol ethylbenzene | | | | | | | | | cis-ethylbenzene | | naphthalene | glycol dehydrogenase | | 1,2-dioxygenase | | | v v v 2,3-Dihydroxy- to the Acetophenone ethylbenzene Styrene Pathway | | | | | | 2,3-dihydroxy- | naphthalene | ethylbenzene | 1,2-dioxygenase | 1,2-dioxygenase | | | v v 2-Hydroxy-6-oxo- 2-Hydroxy- octa-2,4-dienoate acetophenone | | | 2-hydroxy-6-oxo- | octa-2,4-dienoate | hydrolase | v Propanoate + 2-hydroxypenta- | 2,4-dienoate | | | | | | 2-hydroxypenta- | | 2,4-dienoate | | hydratase v | Intermediary v Metabolism 4-Hydroxy-2- (KEGG) oxovalerate | | | 4-hydroxy-2- | oxovalerate | aldolase | v Acetaldehyde + Pyruvate | | | | | | | | | | | | v v Intermediary Intermediary Metabolism Metabolism (KEGG) (KEGG)
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