Biphenyl hydroxylation enhanced by an engineered o-xylene dioxygenase from Rhodococcus sp. strain DK17.

Hydroxylation of the non-growth substrate biphenyl by recombinant o-xylene dioxygenases from Rhodococcus sp. strain DK17 was studied through bioconversion experiments. The metabolites from the biphenyl hydroxylation by each enzyme were identified and quantified by gas chromatography-mass spectrometry. The L266F mutant enzyme produced much more 2-hydroxybiphenyl (2.43 vs. 0.1 μg/L) and 3-hydroxybiphenyl (1.97 vs. 0.03 μg/L) than the wild-type. Site-directed mutagenesis combined with structural and functional analyses indicated that hydrophobic interactions and shielding effects against water are important factors in the hydroxylation of biphenyl by the o-xylene dioxygenase. The residue at position 266 plays a key role in coordinating the reaction.