CP4-EPSPS (Agrobacterium sp. strain CP4 5-enolpyruvylshikimate-3-phosphate synthase) protein showed remarkable thermostability and was highly resistant to proteases, such as trypsin. In order to eliminate the pollution of CP4-EPSPS from the accumulated straws to the surrounding environment during the winter, the present study investigated the extracellular proteases of 21 psychrophilic strains isolated from the south polar region. The results indicated that Stenotrophomonas maltophilia 780 was able to degrade CP4-EPSPS at 18 °C efficiently. Further study indicated that it was able to grow in the extract of Roundup Ready soybean at 18 °C, with CP4-EPSPS degraded to an undetectable level within 72 h. The extracellular proteases of Stenotrophomonas maltophilia 780 are thermo-sensitive, with an optimal temperature of 65 °C. The genomic sequencing result indicated that this strain had more than a hundred putative protease and peptidase coding genes, which may explain its high capability in decomposing CP4-EPSPS.
Keywords: CP4-EPSPS; Stenotrophomonas maltophilia; protease.