Characterization of EstQE, a new member of esterase family VIII from the Quizalofop-p-ethyl (cas 100646-51-3)-degrading bacterium Ochrobactrum sp. QE-9

Add time:08/05/2019    Source:sciencedirect.com

Quizalofop-P-ethyl (QE) is a selective, systemic, post-emergence aryloxyphenoxy propanoate (AOPP) herbicide for the control of annual and perennial grassy weeds in a variety of crops. An efficient QE-degrading bacterial strain, QE-9, was isolated from a QE-manufacturing facility in China and identified as Ochrobactrum sp. A 4.0 kb DNA fragment from QE-9 containing a full length esterase encoding gene was cloned and analyzed. Multiple sequence alignment showed that the esterase gene estqe encoded a 382 amino acid protein that contained the conserved S-X-X-K esterase motif and clustered within esterase family VIII, owning to a lack of beta-lactamase activity. Full-length estqe was amplified by PCR and cloned into plasmid pET-29a for functional expression in Escherichia coli BL21 (DE3). The purified recombinant esterase EstQE converted QE to quizalofop acid (QA) at an optimum temperature and pH of 45 °C and 8.0, respectively. Enzyme activity was severely inhibited by Cu2+, whereas, Ca2+ and Mg2+ significantly increased enzyme activity to 142 and 122% of the control, respectively. The inhibitors PMSF, pCMB, and DEPC as well as detergent SDS strongly inhibited esterase activity. Furthermore, EstQE was capable of hydrolyzing a wide range of other AOPP herbicides, in the following order of catalytic efficiency, quizalofop-P-ethyl > fenoxaprop-P-ethyl > clodinafop-propargyl > cyhalofop-butyl > quizalofop-P-tefuryl > haloxyfop-P-methyl. These results suggest that EstQE is a potential candidate for remediation of AOPP herbicide-contaminated environments.

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