氟铃脲对斜纹夜蛾酚氧化酶活性的影响

【目的】探讨氟铃脲对斜纹夜蛾Spodoptera litura酚氧化酶活性的影响.【方法】应用酶动力学法，在确定斜纹夜蛾酚氧化酶最适反应条件基础上，测定氟铃脲与酚氧化酶直接作用及氟铃脲处理幼虫后酚氧化酶的活性.【结果】以邻苯二酚为底物，斜纹夜蛾酚氧化酶的最适pH 6.5，最适温度30℃.氟铃脲没有和酚氧化酶结构中的铜离子结合，而是直接与酶蛋白发生作用.氟铃脲浓度低于1 153 mg/L对离体酚氧化酶有激活作用，在138 mg/L激活作用最大，浓度高于1 153 mg/L则产生抑制作用.用46 mg/L和92 mg/L亚致死剂量氟铃脲连续处理5龄幼虫不同时间后，酚氧化酶活性均显著提高，且高浓度的激活作用大于低浓度的激活作用.进一步测定药剂处理幼虫24，48和72 h的血淋巴、表皮和头部酚氧化酶活性，随着氟铃脲处理时间延长，两个剂量的氟铃脲对血淋巴、表皮及头部酚氧化酶的激活作用逐渐增大，氟铃脲对血淋巴酚氧化酶的激活作用最大，表皮次之，头部最低.氟铃脲处理幼虫后，其预蛹和蛹酚氧化酶的活性也显著提高，表现出一定的后效应.【结论】一定浓度范围内，氟铃脲对斜纹夜蛾酚氧化酶具有激活作用.

Effects of hexaflumuron on phenoloxidase activity in Spodoptera litura(Fabricius) (Lepidoptera:Noctuidae)

【Objective】To investigate the effects of hexaflumuron on phenoloxidase （PO） activity in the common cutworm, Spodoptera litura（Fabricius） larvae.【Methods】The activities of phenoloxidase directly reacted in vitro with hexaflumuron and that from hexaflumuron-treated 5th instar larvae of S. litura were assayed with enzyme kinetics methods. 【Results】 The optimum reaction conditions of PO were pH 6.5 and best working temperature 30℃ by using catechol as substrate. Hexaflumuron could directly combine with enzyme protein, but it was not chelated with Cu2+ in the active center of PO. The PO activity in vitro increased when hexaflumuron concentrations were below 1 153 mg/L, reached its highest level at 138 mg/L and was inhibited above 1 153 mg/L. After the 5th instar larvae were continuously treated with two sublethal concentrations（46 mg/L and 92 mg/L） of hexaflumuron for different time, the PO activity was significantly higher than that of the control at the same treatment time and the activation rates at high concentrations were larger than that at low concentrations. The PO activity in the hemolymph, cuticle and head of the 5th instar larvae increased with treatment time. The activation rate of PO at the same treatment time was the highest in the hemolymph and the lowest in the head. After the 5th instar larvae were continuously treated with hexaflumuron, PO activities in prepupae and pupae were also significantly enhanced. 【Conclusions】 Hexaflumuron can activate phenoloxidase activity in S. litura.