Aromatic hydroxylation catalyzed by toluene 4-monooxygenase in organic solvent/aqueous buffer mixtures |
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Authors: | Sheldon F. Oppenheim Joey M. Studts Brian G. Fox Jonathan S. Dordick |
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Affiliation: | (1) Department of Chemical Engineering, Rensselaer Polytechnic Institute, 12180 Troy, NY;(2) Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, 53706 Madison, WI |
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Abstract: | Toluene 4-monooxygenase is a four-protein component diiron enzyme complex. The enzyme catalyzes the hydroxylation of toluene to give p-cresol with ∼96% regioselectivity. The performance of the enzyme in two-phase reaction systems consisting of toluene, hexane, or perfluorohexane and an aqueous buffer was tested. In each of the cosolvent systems, containing up to 93% (v/v) of solvent, the enzyme was active and exhibited regioselectivity indistinguishable from the aqueous reaction. Using the perfluorohexane/buffer system, a number of polycyclic aromatic hydrocarbons were oxidized that were not readily oxidized in aqueous buffer. An instability of the hydroxylase component and a substantial uncoupling of NADH utilization and product formation were observed in reactions that were continued for longer than ∼3 min. More stable enzyme complexes will be needed for broad applicability of this hydroxylating system in nonaqueous media. |
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Keywords: | Diiron enzyme monooxygenase organic cosolvents regioselective hydroxylation |
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