Peroxiredoxins (Prxs) are ubiquitously expressed antioxidant proteins that can protect aerobic organisms from oxidative stress. Here, we characterized the HaPrx3 homolog at the molecular level from big-belly seahorse (Hippocampus abdominalis) and analyzed its functional activities. The coding sequence of HaPrx3 consists of 726 bp, which encodes 241 amino acids. The predicted molecular weight and theoretical isoelectric point (pI) of HaPrx3 was 26.20 kDa and 7.04, respectively. Multiple sequence alignments revealed that the arrangements of domains, catalytic triads, dimers, and decamer interfaces of HaPrx3 were conserved among Prx sequences of other organisms. According to the phylogenetic analysis, HaPrx3 is clustered with the teleost Prx3 subclade. The highest transcript level of HaPrx3 was detected in the ovary tissue among fourteen healthy fish tissues. The mRNA levels of HaPrx3 in blood and liver tissues were significantly (P < 0.05) upregulated in response to lipopolysaccharide (LPS), polyinosinic-polycytidylic (poly I:C), Edwardsiella tarda, and Streptococcus iniae, suggesting its involvement in immune responses. Under functional properties, insulin disulfide reduction assay confirmed the oxidoreductase activity of recombinant HaPrx3. A cell viability assay and Hoechst staining indicated cell survival ability and reduction of apoptotic activity, respectively. Moreover, a peroxidase activity assay verified peroxidase activity, while a metal-catalyzed oxidation (MCO) assay indicated the DNA protection ability of HaPrx3. Collectively, it is concluded that HaPrx3 may play a significant role in oxidative stress and immune responses against pathogenic infections in big-belly seahorses.

过氧化物酶（Prxs）是普遍表达的抗氧化剂蛋白，可以保护好氧生物免受氧化应激。在这里，我们从大腹海马（海马腹部）的分子水平上表征了HaPrx3同源物，并分析了其功能活性。HaPrx3的编码序列由726 bp组成，编码241个氨基酸。HaPrx3的预测分子量和理论等电点（pI）分别为26.20 kDa和7.04。多个序列比对揭示，HaPrx3的结构域，催化三联体，二聚体和十聚体界面的排列在其他生物的Prx序列之间是保守的。根据系统发育分析，HaPrx3与硬骨鱼Prx3子簇聚在一起。最高成绩单在十四种健康鱼类组织的卵巢组织中检测到HaPrx3。血脂和肝组织中HaPrx3的mRNA水平显着 上调（P <0.05），这是由于脂多糖（LPS），多肌苷酸-多聚胞苷（poly I：C），爱德华氏菌和印度链球菌引起的，提示其参与了免疫反应。根据功能性质，胰岛素二硫化物还原测定法证实了重组HaPrx3的氧化还原酶活性。细胞活力测定和Hoechst染色分别表明细胞存活能力和凋亡活性降低。此外，过氧化物酶活性测定证实了过氧化物酶活性，而金属催化氧化（MCO）测定表明HaPrx3的DNA保护能力。总体而言，得出的结论是HaPrx3可能在大腹海马的氧化应激和针对病原体感染的免疫应答中起重要作用。