Comparison of glutathione S‐transferase and general esterase in two bugs, Eurygaster integriceps Puton (Heteroptera: Scutelleridae) and Brachynema germari Kolenati (Heteroptera: Pentatomidae)

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AbstractGlutathione S‐transferases (GSTs) and general esterases play important roles in the detoxification of many substances including allelochemicals from plants and chemical pesticides. In this study, to determine the feeding status and effects of agronomical practices on GST and general esterase, two bug species, Eurygaster integriceps and Brachynema germari, were selected with differences in these cases. GST and general esterase responses varied when switching from 1‐chloro‐2,4‐dinitrobenzene (CDNB) and α‐naphtyl to 1,2‐dichloro‐4‐nitro‐benzene (DCNB) and β‐naphtyl in E. integriceps and B. germari, respectively. The activities of GST and esterase by using CDNB and α‐naphtyl were higher than that of DCNB and β‐naphtyl for both insects. It was shown that the optimal pH for GST and general esterase activity varied between pH 5.5 and 6. While the Michaelis constant (Km) value related to E. integriceps toward CDNB and α‐naphtyl was lower than Km for B. germari, Km values calculated for E. integriceps toward DCNB and β‐naphtyl corresponding to those related to A. hejeri were similar to CDNB and α‐naphtyl values. The maximal reaction velocity (Vmax) values related to E. integriceps for both substrates (CDNB and α‐naphtyl) were always higher than those from B. germari and showed significant differences. At the basement of the native‐PAGE electrophoresis, five bands were observed in for GST and three were visualized for B. germari, with a large, darker band for E. integriceps in the case of esterases. Studies on the detoxification enzymes of herbivores should be undertaken to determine accurately the effect of the host plants on the organisms eating them, particularly in terms of biochemical and ecological advantages.