Chen_2025_Biosci.Biotechnol.Biochem__

Haloalkane dehalogenases (HLDs) convert halogenated compounds to corresponding alcohols by a simple hydrolytic mechanism. Although many bacterial strains possess HLDs or HLD homologues, LinB is the only HLD known to be involved in the utilization of gamma-hexachlorocyclohexane (gamma-HCH), a man-made chlorinated pesticide. In this study, to gain insight into the functional evolution of HLDs toward the gamma-HCH utilization, the linB gene in gamma-HCH-degrading Sphingobium japonicum strain UT26 was replaced by 7 other HLD or HLD homologous genes, including 3 putative ancestral enzymes. Interestingly, strains carrying genes for DmmA from marine metagenome or Rluc_anc, an ancestor of Renilla-luciferin 2-monooxygenase (Rluc) and LinB, produced 2,5-dichlorophenol and 2,5-dichlorohydroquinone from gamma-HCH, which are indicators of LinB activity, and grew in minimal medium supplied with gamma-HCH as a sole carbon source. These results indicated that other HLDs in addition to LinB can play roles in the gamma-HCH utilization.