Research on the anti-oxidative stress system in insects

研究了洋葱(Delia Antiqua)幼虫体内超氧化物歧化酶(SOD)活性的变化与幼虫生长及其对氧化胁迫反应的关系。在新孵化的幼虫中，特定的SOD活性非常高，但当它们开始摄食不含植物次生化合物的合成饲料时，其活性迅速下降。相比之下，在喂食洋葱片或其匀浆后的几个小时内，超氧化物歧化酶活性就会增加。由于洋葱乙醇提取物对超氧化物歧化酶活性没有明显影响，因此认为洋葱中的超氧化物歧化酶诱导物(S)是由组织损伤产生的，包括昆虫取食引起的组织损伤。天然分子量估计为32,000。SDS-PAGE仅显示16,000个亚基中的一个亚基，表明超氧化物歧化酶是同源二聚体。等电聚焦发现了PIS5.3、5.5和5.7的3个电荷异构体。纯化后的超氧化物歧化酶比活力为4250单位/mg蛋白。一株抗果蝇SOD的单抗(ASOD2B7)只能识别同属的SOD，而另一株单抗(ASOD1H11)也能识别黑腹果蝇的SOD。

The changes of superoxide dismutase (SOD) activity in the onion maggot, Delia antiqua, were investigated in relation to the growth of larvae and its responsiveness to oxidative stress. Specific SOD activity was very high in the newly hatched larvae, but it decreased rapidly when they started feeding a synthetic diet, which is free from plant secondary compounds. By contrast, SOD activity was increased in a few hours after feeding onion pieces or its homogenate. As ethanol extract of onion had no apparent effect on SOD activity, SOD-inducing compound (s) in onion was considered to be produced by tissue injuries, including those caused by insect feeding.SOD of D.antiqua was purified to apparent homogeneity by ammonium sulfate fractionation, followed by anion exchange, hydrophobic interaction and gel filtration chromatographies. Native molecular weight was estimated as 32,000. SDS-PAGE revealed only one subunit of 16,000, indicating SOD is a homodimer. Isoelectric focusing revealed 3 charge isomers of pIs 5.3,5.5 and 5.7. Specific activity of purified SOD was 4250 units/mg protein. A monoclonal antibody (MAb, aSOD2B7) raised against Delia SOD recognized only SOD of the same genus, but another MAb (aSOD1H11) recognized SOD of Drosophila melanogaster as well.