The thioredoxin domain containing 5 (TXNDC5) is a recently discovered member of the protein disulfide isomerase family (PDI), which is mainly involved in the proper folding of and the correct formation of disulfide bonds in newly synthesized proteins via its disulfide isomerase and chaperone activities. Although the structural and functional features of mammalian TXNDC5 have been explored in previous studies, no studies have reported the functional characteristics of TXNDC5 in teleost fish. In this study, we report the identification and characterization of TXNDC5 from big-belly seahorse (Hippocampus abdominalis) (ShTXNDC5) accompanied by functional studies. The in-silico analysis revealed that the gene encodes a 433 amino acid (aa) long polypeptide chain with a predicted molecular weight of 49.3 kDa. According to homology analysis, ShTXNDC5 shares more than 55% sequence similarity with other teleost TXNDC5 proteins, and the alignment of the gene sequence convincingly reflects the accepted phylogeny of teleost. Analysis of the spatial distribution of ShTXNDC5 expression showed that its highest expression was observed in the ovary, gill, and pouch of seahorses. Moreover, significant upregulation of ShTXNDC5 transcription was noted in seahorse blood and kidney tissues in a time-dependent manner upon viral and bacterial immune challenges. Furthermore, considerable NADPH turnover, insulin reduction ability and significant cell survival effects of ShTXNDC5 were determined by the functional assay, revealing its capability to overcome cellular oxidative stress. Altogether, these findings expand our understanding of TXNDC5 at the molecular and functional levels, and its putative role in seahorse immunity.

含硫氧还蛋白结构域 5 (TXNDC5) 是最近发现的蛋白质二硫键异构酶家族 (PDI) 的成员，主要通过其二硫键异构酶和分子伴侣活性参与新合成蛋白质中二硫键的正确折叠和正确形成. 尽管在以前的研究中已经探索了哺乳动物 TXNDC5 的结构和功能特征，但没有研究报道 TXNDC5 在硬骨鱼中的功能特征。在这项研究中，我们报告了来自大腹海马 ( Hippocampus alienis ) ( ShTXNDC5 ) 的 TXNDC5 的鉴定和表征，并进行了功能研究。计算机内分析显示该基因编码433个氨基酸（aa）长的多肽链，预测分子量为49.3 kDa。根据同源性分析，ShTXNDC5与其他硬骨鱼TXNDC5蛋白的序列相似性超过55%，基因序列的比对令人信服地反映了公认的硬骨鱼系统发育。ShTXNDC5表达的空间分布分析表明，在海马的卵巢、鳃和囊中观察到其最高表达。此外，ShTXNDC5的显着上调在病毒和细菌免疫挑战下，在海​​马血液和肾脏组织中以时间依赖性方式记录了转录。此外，通过功能测定确定了 ShTXNDC5 的相当大的 NADPH 转换、胰岛素降低能力和显着的细胞存活效应，揭示了其克服细胞氧化应激的能力。总之，这些发现扩展了我们在分子和功能水平上对 TXNDC5 的理解，以及它在海马免疫中的假定作用。