Department of Entomology, China Agricultural University, Beijing 100193, China.
J Immunol Res. 2016;2016:1781803. doi: 10.1155/2016/1781803. Epub 2016 Dec 18.
Insect phenoloxidase (PO) belongs to the type 3 copper protein family and possesses oxidoreductase activities. PO is typically synthesized as a zymogen called prophenoloxidase (PPO) and requires the proteolytic activation to function. We here cloned full-length cDNA for 3 previously unidentified PPOs, which we named OfPPO1a, OfPPO1b, and OfPPO3, from Asian corn borer, (Gunée), in addition to the previously known OfPPO2. These conceptual PPOs and OfPPO2 all contain two common copper-binding regions, two potential proteolytic activation sites, a plausible thiol-ester site, and a conserved C-terminal region but lack a secretion signal peptide sequence at the N-terminus. PPOs were highly similar to other insect PPOs (42% to 79% identity) and clustered well with other lepidopteran PPOs. RT-PCR assay showed the transcripts of the 4 OfPPOs were all detected at the highest level in hemocytes and at the increased amounts after exposure to infection by bacteria and fungi. Additionally, we established an () expression system to produce recombinant PPO proteins for future use in investigating their functions. These insights could provide valuable information for better understanding the activation and functioning mechanisms of PPOs.
昆虫酚氧化酶 (PO) 属于第三类铜蛋白家族，具有氧化还原酶活性。PO 通常作为一种称为原酚氧化酶 (PPO) 的酶原合成，并需要蛋白水解激活才能发挥作用。我们在这里从亚洲玉米螟中克隆了全长 cDNA 的 3 种以前未鉴定的 PPO，分别命名为 OfPPO1a、OfPPO1b 和 OfPPO3，除了先前已知的 OfPPO2。这些概念性的 PPO 和 OfPPO2 都含有两个常见的铜结合区域、两个潜在的蛋白水解激活位点、一个合理的硫酯位点和一个保守的 C 末端区域，但在 N 末端缺乏分泌信号肽序列。PPO 与其他昆虫 PPO 高度相似（42%到 79%的同一性），并与其他鳞翅目 PPO 聚类良好。RT-PCR 检测显示，这 4 种 OfPPO 的转录本在血细胞中表达水平最高，在暴露于细菌和真菌感染后表达量增加。此外，我们建立了一个 () 表达系统来生产重组 PPO 蛋白，以便将来用于研究它们的功能。这些发现可以为更好地理解 PPO 的激活和作用机制提供有价值的信息。
