栎皮酮对甜菜夜蛾酚氧化酶的抑制作用

Inhibitory effect of quercetin on the activity of phenoloxidase in Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae)

研究了栎皮酮对甜菜夜蛾Spodopteraexigua酚氧化酶活力的影响。结果表明 :栎皮酮对该虫的单酚酶和二酚酶活性均表现很强的抑制作用 ,其I50 分别为 0 0 79mmol L和 0 0 87mmol L。其中 ,栎皮酮对单酚酶活力表达的迟滞时间有明显的延长效应 ,浓度为 0 0 79mmol L时可使单酚酶活力表达迟滞时间从 134s延长到 330s;而当浓度为 0 15 8mmol L时 ,其迟滞时间则延长至 4 4 0s。以L 多巴为底物时 ,栎皮酮对二酚酶的抑制作用表现为典型的竞争型抑制类型 ,抑制常数Ki 为 33 16mmol L。在研究金属离子对栎皮酮吸收峰影响实验中发现 ,Cu2 + 对吸收峰影响最大 ,可使栎皮酮最大吸收波长从 36 7nm改变为 4 35nm ;而加入Mg2 + 与Ca2 + 后 ,其最大吸收峰却无明显的偏移。

The inhibition to monophenolase and o-diphenolase activity of phenoloxidase (PO) in Spodoptera exigua (Lepidoptera: Noctuidae) by quercetin was studied. The results showed that the I_(50) were estimated to be 0.079 mmol/L for monophenolase activity and 0.087 mmol/L for diphenolase, respectively. Quercetin extended the lag time of the enzyme for oxidation of L-tyrosine. In 0.079 mmol/L the natural source compound resulted in the lag time extension from 134 s to 330 s; in 0.158 mmol/L the compound resulted in the lag time extension from 134 s to 440 s. The results of inhibition kinetics analyzed by Lineweaver-Burk plots indicated that quercetin was a competitive inhibitor for the oxidation of L-DOPA, and the inhibition constant was determined to be 33.16 mmol/L. The bathochromic shift was observed with quercetin (367-435 nm) by adding excess Cu^(2+), and this shift was not observed by adding excess Ca^(2+) or Mg^(2+).