黄粉虫幼虫体壁硬化过程中酚氧化酶活性的变化

为研究酚氧化酶(PO)在昆虫蜕皮过程中的功能和作用, 采用微量测定法研究了黄粉虫Tenebrio molitor体壁硬化过程中血淋巴和表皮中的PO活性变化。结果表明：初蜕皮幼虫血淋巴中PO活性较高, 但随着体壁的不断黑化与硬化, 其活性呈现下降趋势, 在3～4 h内达到最低点, 而后PO活性逐渐上升, 7 h左右活性上升至最高, 并接近于正常幼虫的水平；在刚蜕完皮后的1 h内, 体壁中 PO活性基本无变化, 但随后即开始下降, 3 h左右降到最低点, 然后开始回升, 6~7 h左右恢复到正常水平, 并趋于稳定；以L-DOPA为底物, 通过双倒数曲线作图法求得黄粉虫血淋巴PO的Km＝1.176 mmol/L, 体壁PO的Km＝0.881 mmol/L, 表明体壁PO与底物L-DOPA的亲和力要高于血淋巴PO。研究表明两种来源的酚氧化酶均参与了黄粉虫幼虫的体壁硬化过程, 但在作用方式及与底物的亲和力方面存在差异。

Phenoloxidase activity during cuticle sclerotization in larvae of Tenebrio molitor (Coleoptera: Tenebrionidae)

The activity of phenoloxidase (PO) from the hemolymph and cuticle of Tenebrio molitor larvae was investigated at different time (1 -7 h) after molting with the microtitration method. The results showed that the hemolymph PO activity slowly decreased within 3 h after the larva molted but increased at 4 - 7 h after molting. The cuticle PO activity showed no remarkable changes within 1 h after the larva molted, but decreased at 3 h after molting. The PO activity nearly reached the normal level at 6 h after the larva molted. Meanwhile, determined by Lineweaver-Burk plot the K_m value of PO extracted from the hemolymph and cuticle was 1. 176 and 0. 881 mmol/L, respectively, indicating that PO from the cuticle has a higher affinity to substrate than that from the hemolymph. The results showed that both cuticle and hemolymph PO were involved in cuticle sclerotization of T. molitor, but have differences in action mode and affinity to substrate.