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Benzylic and aryl hydroxylations of m-xylene by o-xylene dioxygenase from Rhodococcus sp. strain DK17.
- Source :
- Applied Microbiology & Biotechnology; May2010, Vol. 86 Issue 6, p1841-1847, 7p, 2 Diagrams, 1 Chart, 1 Graph
- Publication Year :
- 2010
-
Abstract
- Escherichia coli cells expressing Rhodococcus DK17 o-xylene dioxygenase genes were used for bioconversion of m-xylene. Gas chromatography–mass spectrometry analysis of the oxidation products detected 3-methylbenzylalcohol and 2,4-dimethylphenol in the ratio 9:1. Molecular modeling suggests that o-xylene dioxygenase can hold xylene isomers at a kink region between α6 and α7 helices of the active site and α9 helix covers the substrates. m-Xylene is unlikely to locate at the active site with a methyl group facing the kink region because this configuration would not fit within the substrate-binding pocket. The m-xylene molecule can flip horizontally to expose the meta-position methyl group to the catalytic motif. In this configuration, 3-methylbenzylalcohol could be formed, presumably due to the meta effect. Alternatively, the m-xylene molecule can rotate counterclockwise, allowing the catalytic motif to hydroxylate at C-4 yielding 2,4-dimethylphenol. Site-directed mutagenesis combined with structural and functional analyses suggests that the alanine-218 and the aspartic acid-262 in the α7 and the α9 helices play an important role in positioning m-xylene, respectively. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 01757598
- Volume :
- 86
- Issue :
- 6
- Database :
- Complementary Index
- Journal :
- Applied Microbiology & Biotechnology
- Publication Type :
- Academic Journal
- Accession number :
- 49746522
- Full Text :
- https://doi.org/10.1007/s00253-009-2418-5