Hydrolysis mechanism of carbendazim hydrolase from the strain Microbacterium sp. djl-6F.

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.