七种抑制剂对两种白蚁谷胱甘肽S-转移酶活性抑制作用的比较

利用分光光度酶动力学方法，确定了白蚁谷胱甘肽S-转移酶（GSTs）的最适反应条件，并进一步研究了7种抑制剂对黑翅土白蚁Odontotermes formosanus (Shiraki)和黑胸散白蚁Reticulitermes chinensis Snyder GSTs活性的体外影响。结果表明：白蚁GSTs测定的最适反应条件为pH 6.5，温度25℃，最适反应时间2 min。黑翅土白蚁GSTs的米氏常数(K_mCDNB和K_mGSH)分别为0.11±0.02 mmol/L和0.81±0.16 mmol/L，最大反应速度(V_maxCDNB和V_maxGSH)分别为425.92±19.67 nmol/(min·mg)和534.86±39.05 nmol/(min·mg)。黑胸散白蚁GSTs的米氏常数(K_mCDNB和K_mGSH)分别为0.12±0.03 mmol/L和1.03±0.31 mmol/L，最大反应速度(V_maxCDNB和V_maxGSH)分别为544.39±37.19 nmol/(min·mg)和715.45±83.68 nmol/(min·mg)。浓度为2×10^-5 mol/L时，槲皮素和辛硫磷对黑胸散白蚁GSTs活性的抑制作用要强于黑翅土白蚁，对黑胸散白蚁GSTs活性的抑制作用分别为62.28％和44.89％，对黑翅土白蚁GSTs活性的抑制作用分别为54.96％和28.36％。高效氯氰菊酯、甲氰菊酯、啶虫脒和单宁酸对黑翅土白蚁GSTs活性的抑制作用要强于黑胸散白蚁，对黑翅土白蚁GSTs活性的抑制作用分别为39.43％，72.07％，52.24％和82.19％；对黑胸散白蚁GSTs活性的抑制作用分别为14.96％，40.23％，39.96％和57.80％。阿维菌素对黑翅土白蚁和黑胸散白蚁GSTs活性的抑制作用没有显著差异，对黑翅土白蚁和黑胸散白蚁GSTs活性的抑制作用分别为76.21％和76.88％。这表明两种白蚁对药剂的敏感性完全不同。实验结果还表明，在3.2×10^-8～2×10^-5 mol/L内，上述植物次生物质和杀虫剂对两种白蚁GSTs活性的抑制率存在明显的剂量-效应关系。

Inhibition of glutathion S-transferases activity from Odontotermes formosanus (Shiraki) and Reticulitermes chinensis Snyder by seven inhibitors

The optimum reaction condition of glutathion S- transferases (GSTs) in termites was studied using the biochemistry methods. Furthermore, the inhibition of GSTs from Odontotermes formosanus (Shiraki) and Reticulitermes chinensis Snyder by seven inhibitors (quercetin, tannic acid, abamectin, fenpropathrin, acetamiprid, phoxim, beta-cypermethrin), were determined. The results indicated that the optimum pH value was 6.5, the optimum reaction time was 2 min, and the optimum temperature was 25℃ for GSTs in termites. The Michaelis constant (K_mCDNB and K_mGSH) of GSTs hydrolyzing CDNB and GSH were 0.11±0.02 mmol/L and 0.81±0.16 mmol/L in O. formosanus, respectively, not significantly different from that of GSTs in R. chinensis (0.12±0.03 mmol/L and 1.03±0.31 mmol/L). The maximum velocities (V_maxCDNB and V_maxGSH) hydrolyzing CDNB and GSH were 425.92±19.67 nmol/(min·mg) and 534.86±39.05 nmol/(min·mg) for O. formosanus， and 544.39±37.19 nmol/(min·mg) and 715.45±83.68 nmol/(min·mg) for R. chinensis, respectively. When the final concentration of plant allelochemicals and insecticides was 2×10^-5 mol/L, inhibition to GSTs from R. chinensis by quercetin and phoxim was stronger than to that from O. formosanus. The percentage of inhibition of GSTs activity from R. chinensis was 62.28% and 44.89％, and the percentage of inhibition of GSTs from O. formosanus was 54.96% and 28.36％ by the above plant allelochemicals and insecticides, respectively, when the concentration of inhibitors was 2×10^-5 mol/L. When the final concentration of plant allelochemicals and insecticides was 2×10^-5 mol/L, inhibition to GSTs from O. formosanus by beta-cypermethrin, fenpropathrin, acetamiprid and tannic acid was stronger than to that from R. chinensis. The percentage of inhibition of GSTs activity from O. formosanus was 39.43%, 72.07%, 52.24% and 82.19%, and the percentage of inhibition of GSTs from R. chinensis was 14.96%, 40.23%, 39.96% and 57.80％by the above plant allelochemicals and insecticides, respectively, when the concentration of inhibitors was 2×10^-5 mol/L. There was no difference in the percentage of inhibition of the activity of GSTs from O. formosanus and R. chinensis when the concentration of abamectin was 2×10^-5 mol/L. The results suggested that the difference in GST sensitivity to insecticides existed between the two termites. Furthermore, the inhibition of GST activity by plant allelochemicals and insecticide was increased with the increasing of insecticide concentration from 3.2×10^-8 to 2×10^-5 mol/L.