Over-expression and Purification of Recombinant Methylparathion Degrading Enzyme by Lactose Induction

Organophosphorus (OP) degrading enzymes were widely used in economical and safe detoxification of organophosphorus pesticides from soil, water, food, and aquatic product. In this study, a novel methylparathion degrading enzyme (MPD) was over-expressed in Escherichia coli BL21 (DE3) as a His-tagged fusion protein by the use of lactose as inducer instead of IPTG. SDS-PAGE combined with enzyme activity analysis indicated that lactose-induced expression yield of active MPD was increased nearly 2-fold compared with IPTG as inducer. The optimum temperature and concentration for lactose induction was 37 degrees C and 0.5 % (w/v), respectively. The expressed fusion proteins induced by the two inducers were both purified by Ni-metal-affinity chromatography. The specific activity of the purified recombinant MPD induced by lactose, reaching at 140 mu mol.min(-1).mg(-1), was nearly 0.5-fold higher than that of the purified enzyme induced by IPTG. Thus, lactose was a well alternative inducer to produce active MPD and gave an advantage over enzyme purification. This study suggested a more effective method to produce purified MPD, an ideal enzyme to detoxify OP pesticides for ecosystem restoration.