Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Special Self-Governing Province 690-756, Republic of Korea.
Fish Shellfish Immunol. 2012 Oct;33(4):753-65. doi: 10.1016/j.fsi.2012.06.024. Epub 2012 Jul 10.
Superoxide dismutases (SODs), antioxidant metalloenzymes, represent the first line of defense in biological systems against oxidative stress caused by excessive reactive oxygen species (ROS), in particular O(2)(•-). Two distinct members of SOD family were identified from Manila clam Ruditapes philippinarum (abbreviated as RpMnSOD and RpCu/ZnSOD). The structural analysis revealed all common characteristics of SOD family in both RpSODs from primary to tertiary levels, including three MnSOD signatures and two Cu/ZnSOD signatures as well as invariant Mn(2+)- and Cu/Zn(2+)-binding sites in RpMnSOD and RpCu/ZnSOD, respectively. Putative RpMnSOD and RpCu/ZnSOD proteins were predicted to be localized in mitochondrial matrix and cytosol, respectively. They shared 65.2% and 63.9% of identity with human MnSOD and Cu/ZnSOD, respectively. Phylogentic evidences indicated the emergence of RpSODs within molluscan monophyletic clade. The analogous spatial expression profiles of RpSODs demonstrated their higher mRNA levels in hemocytes and gills. The experimental challenges with poly I:C, lipopolysaccharide and Vibrio tapetis illustrated the time-dependent dynamic expression of RpSODs in hemocytes and gills. The recombinant RpMnSOD was expressed in a prokaryotic system and its antioxidant property was studied. The rRpMnSOD exhibited its optimum activity at 20 °C, under alkaline condition (pH 9) with a specific activity of 3299 U mg(-1). These outcomes suggested that RpSODs were constitutively expressing inducible proteins that might play crucial role(s) in innate immunity of Manila clam.
超氧化物歧化酶（SOD）是抗氧化金属酶，是生物系统抵御活性氧（ROS）引起的氧化应激的第一道防线，特别是 O(2)(•-)。从菲律宾蛤仔（Ruditapes philippinarum）中鉴定出两种不同的 SOD 家族成员（缩写为 RpMnSOD 和 RpCu/ZnSOD）。结构分析揭示了 RpSODs 在一级到三级结构上都具有 SOD 家族的所有共同特征，包括三个 MnSOD 特征和两个 Cu/ZnSOD 特征，以及 RpMnSOD 和 RpCu/ZnSOD 中分别不变的 Mn(2+)和 Cu/Zn(2+)结合位点。推测 RpMnSOD 和 RpCu/ZnSOD 蛋白分别定位于线粒体基质和细胞质中。它们与人类 MnSOD 和 Cu/ZnSOD 的同源性分别为 65.2%和 63.9%。系统发育证据表明，RpSODs 出现在软体动物单系群中。 RpSODs 类似的空间表达谱表明，它们在血细胞和鳃中的 mRNA 水平更高。用聚 I:C、脂多糖和 Vibrio tapetis 进行实验挑战，说明了 RpSODs 在血细胞和鳃中的时间依赖性动态表达。重组 RpMnSOD 在原核系统中表达，并研究了其抗氧化特性。rRpMnSOD 在 20°C、碱性条件（pH 9）下表现出最佳活性，比活为 3299 U mg(-1)。这些结果表明，RpSODs 是组成型表达的诱导蛋白，可能在菲律宾蛤仔的先天免疫中发挥关键作用。
