Degradation of β-hexachlorocyclohexane by haloalkane dehalogenase LinB from γ-hexachlorocyclohexane-utilizing bacterium Sphingobium sp. MI1205

Michihiro Ito, Zbyňek Prokop, Martin Klvaňa, Yoshiyuki Otsubo, Masataka Tsuda, Jiří Damborský, Yuji Nagata

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

The technical formulation of hexachlorocyclohexane (HCH) mainly consists of the insecticidal γ-isomer and noninsecticidal α-, β-, and δ-isomers, among which β-HCH is the most recalcitrant and has caused serious environmental problems. A γ-HCH-utilizing bacterial strain, Sphingobium sp. MI1205, was isolated from soil which had been contaminated with HCH isomers. This strain degraded β-HCH more rapidly than the well-characterized γ-HCH-utilizing strain Sphingobium japonicum UT26. In MI1205, β-HCH was converted to 2,3,5,6-tetrachlorocyclohexane-1,4-diol (TCDL) via 2,3,4,5,6-pentachlorocyclohexanol (PCHL). A haloalkane dehalogenase LinB (LinBMI) that is 98% identical (seven amino-acid differences among 296 amino acids) to LinB from UT26 (LinBUT) was identified as an enzyme responsible for the two-step conversion of β-HCH to TCDL. This property of LinBMI contrasted with that of LinBUT, which catalyzed only the first step conversion of β-HCH to PCHL. Site-directed mutagenesis and computer modeling suggested that two of the seven different amino acid residues (V134 and H247) forming a catalytic pocket of LinB are important for the binding of PCHL in an orientation suitable for the reaction in LinBMI. However, mutagenesis also indicated the involvement of other residues for the activity unique to LinBMI. Sequence analysis revealed that MI1205 possesses the IS6100-flanked cluster that contains two copies of the linB MI gene. This cluster is identical to the one located on the exogenously isolated plasmid pLB1, suggesting that MI1205 had recruited the linB genes by a horizontal transfer event.

Original languageEnglish
Pages (from-to)313-325
Number of pages13
JournalArchives of Microbiology
Volume188
Issue number4
DOIs
Publication statusPublished - 2007 Oct

Keywords

  • Environmental pollutant
  • Haloalkane dehalogenase
  • Hexachlorocyclohexane
  • Sphingomonads

ASJC Scopus subject areas

  • Microbiology
  • Biochemistry
  • Molecular Biology
  • Genetics

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