Glutathione-S-transferase (GST) catalyzes the degradation of Chlorimuron-ethyl by Klebsiella jilinsis 2N3

Abstract

Microbial degradation is one of the most efficient and reliable ways to remove the residues of Chlorimuron-ethyl in the environments such as soil and water. In this study, a glutathione-s-transferase (GST) gene Kj-gst was cloned from the Chlorimuron-ethyl degrading bacterial strain Klebsiella jilinsis 2N3. Results showed that Kj-gst played a key role in the degradation of Chlorimuron-ethyl by strain 2N3. The mutant with gene Kj-gst knocked out showed reduced relative activity up to 70% compared with the wild type in 8 h in culture. After the knockout gene was complemented, the degradation ability of the complement mutant was essentially comparable to that of the wild type. The protein Kj-GST (50 μg) obtained from the gene Kj-gst expressed and purified in E. coli strain BL21(DE3) was capable of degrading Chlorimuron-ethyl with an initial concentration of 50 mg/mL by 42.91% under the optimal conditions (15 °C and pH = 7). Point mutation experiments on a glycine located at position 101 (Glu101) confirmed that the H site of glutathione (GSH) is the key component in Kj-GST for degrading Chlorimuron-ethyl. We conclude that Kj-GST is demonstrated for the first time to degrade Chlorimuron-ethyl with its main functional site identified at the H site of GSH, shedding insight to revealing the molecular mechanisms of degrading Chlorimuron-ethyl by Klebsiella jilinsis 2N3.