环境激素甲草胺对摇蚊谷胱甘肽硫转移酶的抑制作用

谷胱甘肽硫转移酶(GST)是生物体内重要的解毒酶。为研究环境激素甲草胺对溪流摇蚊GST的抑制作用及机理,采用酶标仪微量法测定甲草胺对溪流摇蚊4龄幼虫GST的抑制活性及抑制类型。结果表明甲草胺在72 h活体染毒和离体状态下均能显著抑制溪流摇蚊GST的活性,且抑制程度随着药物浓度的增大而增大。甲草胺抑制GST活性的反应为可逆性抑制。进一步的酶动力学分析揭示甲草胺对GST的特异底物1-氯-2,4-二硝基苯(CDNB)和还原型谷胱甘肽(GSH)均表现为竞争性抑制,即甲草胺仅影响米氏常数(Km),不改变酶促反应的最大反应速度(Vmax)。以上结果表明农药残留污染物甲草胺在胁迫下对摇蚊幼虫GST酶活性会受到显著影响,甲草胺对GST的抑制机制为可逆性和竞争性抑制。

Inhibition Effect of Alachlor on Glutathione S-transferase of Chironomus riparius (Diptera: Chironomidae)

Glutathione S-transferases (GST) is an important detoxi?cation enzyme of the organisms. To investigate the inhibition effect and the mechanism of the environmental hormone pesticide alachlor against GST of Chironomus riparius, the inhibition activity and inhibition type of alachlor against fourth-instar larvae of C. riparius were determined by microtitration assay. The results showed that alachlor significantly inhibited GST activities both in vivo 72 h exposure and in vitro, and the inhibition degree increased in an alachlor concentration-dependent manner. The inhibition reaction of alachlor on GST was reversible. Further analysis of enzyme kinetics revealed that the inhibition was competitive with specific substrate of 1-chloro-2,4- dinitrobenzene (CDNB) and reduced Glutathione (GSH), that was to say that alachlor did not change the V_m value of enzymatic reaction, but affected the michaelis constant (K_m). These results suggested that the GST activities of aquatic midge could be significantly affected by the pesticide residue of alachlor, while the inhibition mechanism of alachlor on GST was reversible and competitive.