A complementary DNA that encodes an omega-class glutathione S-transferase (GST) of the brown planthopper, Nilaparvata lugens (nlGSTO), was isolated by reverse transcriptase polymerase chain reaction. A recombinant protein (nlGSTO) was obtained via overexpression in the Escherichia coli cells and purified. nlGSTO catalyzes the biotransformation of glutathione with 1-chloro-2,4-dinitrobenzene, a general substrate for GST, as well as with dehydroascorbate to synthesize ascorbate. Mutation experiments revealed that putative substrate-binding sites, including Phe28, Cys29, Phe30, Arg176, and Lue225, were important for glutathione transferase and dehydroascorbate reductase activities. As ascorbate is a reducing agent, nlGSTO may participate in antioxidant resistance.
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