Roles of Hydrophobic Interactions in the Hydroxylation of Biphenyl by o-Xylene Dioxygenase from Rhodococcus sp. Strain DK17

Abstract

Bioconversion experiments were performed against the non-growth substrates biphenyl using recombinant o-xylene dioxygenases from Rhodococcus sp. strain DK17. Hydroxylation metabolites of biphenyl by each enzyme were identified and quantified by a gas chromatography-mass spectrometry. The mutant enzyme with the substitution of L266 to phenylalanine produced approximately 24 and 66 times as much 2 hydroxybiphenyl and 3-hydroxybiphenyl as the wild type, respectively. Further site-directed mutagenesis combined with structural and functional analyses indicates that hydrophobic interactions and shielding effects against water as important factors in the hydroxylation of biphenyl by the DK17 o xylene dioxygenase and that the residue at the position 266 plays a key role in such coordination.