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Hydrolysis mechanism of carbendazim hydrolase from the strain Microbacterium sp. djl-6F
Ji Lei1, Shaopeng Wei1, Lijun Ren2
1Key Laboratory of Disaster Survey and Mechanism Simulation of Shaanxi Province, College of Chemistry and Chemical Engineering, Baoji University of Arts and Sciences, Shaanxi, Baoji 721013, China; College of Resources and Environment, College of Life Sciences and College of Plant Protection, Northwest A&F University, Shaanxi, Yangling 712100, China.
Abstract:
The carbendazim (MBC) hydrolyzing enzyme gene was cloned and heterologously expressed in Escherichia coli BL21 (DE3) from a newly isolated MBC-degrading bacterium strain Microbacterium sp. strain djl-6F. High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis revealed that purified MheI-6F protein catalyzes direct hydrolysis of MBC into 2-aminobenzimidazole (2-AB) with a high turnover rate and moderate affinity (Km of 6.69μmol/L and kcat of 160.88/min) without the need for any cofactors. The optimal catalytic condition of MheI-6F was identified as 45°C, pH7.0. The enzymatic activity of MheI-6F was found to be diminished by metal ions, and strongly inhibited by sodium dodecyl sulfate (SDS). Through generating amino acid mutations in MheI-6F, Cys16 and Cys222 were identified as the catalytic groups that are essential for the hydrolysis of MBC. This is the first report on the biodegradation of MBC at the enzymatice level.