Molecular control of phenoloxidase-induced melanin synthesis in an insect
Molecular control of phenoloxidase-induced melanin synthesis in an insect
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DOI：
10.1074/jbc.m804364200
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发表时间：
2008-09-12
影响因子：
4.8
通讯作者：
Lee, Bok Luel
中科院分区：
文献类型：
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作者：
Kan, Hongnan;Kim, Chan-Hee;Lee, Bok Luel
节肢动物活化的酚氧化酶诱导的黑化反应，由于醌类的过量生成和对宿主的系统性黑化损伤过大，必须严格控制。然而，在体内调节酚氧化酶诱导的黑色素合成的分子机制在很大程度上是未知的。众所周知，在果蝇Toll通路中，Spatzle加工酶是由pro-Spatzle产生裂解型Spatzle的关键酶。在这里，我们提供了生化证据，证明黄粉虫molitor Spatzle加工酶将79-kDa黄粉虫酚氧化酶和黄粉虫剪切结构域SPH1酶原转化为活性黑素化复合物。该复合物由76-kDa的黄粉虫酚氧化酶和黄粉虫clip-domain SPH1的活性形式组成，在细菌表面有效地产生黑色素，这种活性具有很强的杀菌作用。有趣的是，我们发现酚氧化酶诱导的黑化反应受到黄粉虫酚氧化酶的严格调控，黄粉虫酚氧化酶是黑化复合物形成的竞争性抑制剂。这些结果表明，黄粉虫Toll通路和黑化反应有一个共同的丝氨酸蛋白酶来调节这两种主要的先天免疫反应。
The melanization reaction induced by activated phenoloxidase in arthropods must be tightly controlled because of excessive formation of quinones and excessive systemic melanization damage to the hosts. However, the molecular mechanism by which phenoloxidase-induced melanin synthesis is regulated in vivo is largely unknown. It is known that the Spatzle-processing enzyme is a key enzyme in the production of cleaved Spatzle from pro-Spatzle in the Drosophila Toll pathway. Here, we provide biochemical evidence that the Tenebrio molitor Spatzle processing enzyme converts both the 79-kDa Tenebrio prophenoloxidase and Tenebrio clip-domain SPH1 zymogen to an active melanization complex. This complex, consisting of the 76-kDa Tenebrio phenoloxidase and an active form of Tenebrio clip-domain SPH1, efficiently produces melanin on the surface of bacteria, and this activity has a strong bactericidal effect. Interestingly, we found the phenoloxidase- induced melanization reaction to be tightly regulated by Tenebrio prophenoloxidase, which functions as a competitive inhibitor of melanization complex formation. These results demonstrate that the Tenebrio Toll pathway and the melanization reaction share a common serine protease for the regulation of these two major innate immune responses.