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Substrate and inhibitor spectra of ethylbenzene dehydrogenase: perspectives on application potential and catalytic mechanism.

Applied and environmental microbiology (2012-07-10)
Daniel Knack, Corina Hagel, Maciej Szaleniec, Agnieszka Dudzik, Aleksander Salwinski, Johann Heider
ABSTRACT

Ethylbenzene dehydrogenase (EbDH) catalyzes the initial step in anaerobic degradation of ethylbenzene in denitrifying bacteria, namely, the oxygen-independent hydroxylation of ethylbenzene to (S)-1-phenylethanol. In our study we investigate the kinetic properties of 46 substrate analogs acting as substrates or inhibitors of the enzyme. The apparent kinetic parameters of these compounds give important insights into the function of the enzyme and are consistent with the predicted catalytic mechanism based on a quantum chemical calculation model. In particular, the existence of the proposed substrate-derived radical and carbocation intermediates is substantiated by the formation of alternative dehydrogenated and hydroxylated products from some substrates, which can be regarded as mechanistic models. In addition, these results also show the surprisingly high diversity of EbDH in hydroxylating different kinds of alkylaromatic and heterocyclic compounds to the respective alcohols. This may lead to attractive industrial applications of ethylbenzene dehydrogenase for a new process of producing alcohols via hydroxylation of the corresponding aromatic hydrocarbons rather than the customary procedure of reducing the corresponding ketones.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ethylbenzene, anhydrous, 99.8%
Supelco
Ethylbenzene, analytical standard
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Ethylbenzene, ReagentPlus®, 99%
Supelco
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), TMS 0.01 %, NMR tube size 5 mm × 8 in.
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Ethylbenzene solution, certified reference material, 5000 μg/mL in methanol
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 10% in chloroform-d (99.8 atom % D)
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 1% in chloroform-d (99.8 atom % D)
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), TMS 0.01 %, NMR tube size 5 mm × 8 in. , ultra-thin wall
Supelco
Ethylbenzene solution, NMR reference standard, 10% in chloroform-d (99.8 atom % D), NMR tube size 5 mm × 8 in. , ultra-thin wall
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 10% in chloroform-d (99.8 atom % D), NMR tube size 10 mm × 8 in.
Supelco
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), NMR tube size 5 mm × 8 in.
Supelco
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), NMR tube size 3 mm × 8 in.
Supelco
Ethylbenzene solution, NMR reference standard, 10% in chloroform-d (99.8 atom % D), NMR tube size 3 mm × 8 in.
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), TMS 0.1 %
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 5% in chloroform-d (99.8 atom % D), TMS 1 %, NMR tube size 5 mm × 7 in.
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d ("100%", 99.96 atom % D)
Supelco
Ethylbenzene solution, NMR reference standard, 5% in chloroform-d (99.8 atom % D), TMS 2 %, NMR tube size 3 mm × 8 in.
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), TMS 0.01 %, NMR tube size 10 mm × 8 in.
Supelco
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), chromium(III) acetylacetonate 0.1 mg/mL, TMS 0.01 %, NMR tube size 5 mm × 8 in.
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), TMS 0.01 %, NMR tube size 8 mm × 8 in.
Sigma-Aldrich
Ethylbenzene solution, NMR reference standard, 5% in chloroform-d (99.8 atom % D), TMS 2 %, NMR tube size 5 mm × 8 in.
Supelco
Ethylbenzene solution, NMR reference standard, 0.1% in chloroform-d (99.8 atom % D), TMS 0.01 %, NMR tube size 3 mm × 8 in.