Benzylic and aryl hydroxylations of m-xylene by o-xylene dioxygenase from Rhodococcus sp. strain DK17

Dockyu Kim, Ki Young Choi, Miyoun Yoo, Jung Nam Choi, Choong Hwan Lee, Gerben J. Zylstra, Beom Sik Kang, Eungbin Kim

Research output: Contribution to journalArticle

11 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)1841-1847
Number of pages7
JournalApplied Microbiology and Biotechnology
Volume86
Issue number6
DOIs
Publication statusPublished - 2010 May 1

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Applied Microbiology and Biotechnology

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