Expression, purification and functional characterization of a recombinant 2,3-dihydroxybiphenyl-1,2-dioxygenase from Rhodococcus rhodochrous

A 2,3-dihydroxybiphenyl (2,3-DHBP) dioxygenase gene from a Rhodococcus sp. strain, named RrbphCI and involved in the degradation of polychlorinated biphenyls (PCBs), was synthesized. RrbphCI was expressed in Escherichia coli and its encoded enzyme was purified. SDS–PAGE analysis indicated that the size of the protein encoded by RrbphCI was about 32 kDa. The activity of the 2,3-DHBP dioxygenase was 82.8 U/mg when the substrate was 2,3-DHBP, with optimum pH 8.0 at 30°C, and optimum temperature was 40°C at pH 8.0. The RrbphCI gene was transformed into Pseudomonasputida strain EG11, to determine the ability of the enzyme to degrade 2,3-DHBP. The wild type EG11 degraded 61.86% of supplied 2,3-DHBP and the transformed EG11 (hosting the RrbphCI gene) utilized 52.68% after 2 min of treatment at 30°C. The overexpressed and purified enzyme was able to degrade 2,3-DHBP. The 2,3-DHBP dioxygenase is a key enzyme in the PCB degradation pathway. RrbphCI and its encoded 2,3-DHBP dioxygenase may have transgenic applications in bioremediation of PCBs.