Characterizations of intracellular copper/zinc superoxide dismutase from yellow drum (Nibea albiflora, Richardson 1846) and its gene expressions under the ammonia/nitrite stress

•Identified the cDNA of na-iccuznsod from yellow drum (Nibea albiflora, Richardson 1846) for the first time.•Obtained the Na-icCuZnSOD fusion protein with high enzyme stabilities over a wide range of temperature (10 to 60 ℃) and pH (4.9 to 11.0).•Giving a new perspective to the study of the structure-function relationship between icCuZnSOD and ecCuZnSOD.•Making it clear how the mRNA transcriptions of na-iccuznsod in yellow drum respond to acute ammonia-N/nitrite-N exposure. Intracellular copper/zinc superoxide dismutase (icCuZnSOD) is a member of superoxide dismutase family that is capable of catalyzing the superoxide radicals into either hydrogen peroxide (H2O2) or ordinary molecular oxygen (O2). Unlike mammals, the study of icCuZnSOD in aquatic animals is still in the infancy stage. Here, we identified the cDNA of na-iccuznsod from yellow drum (Nibea albiflora, Richardson 1846) and obtained its fusion protein for the first time. The mRNA expressions of na-iccuznsod were investigated in different tissues, and the dominant distribution was found in head-kidney, followed by brain, liver, heart, and gill. The effects of ammonia-N/nitrite-N on the mRNA expressions of na-iccuznsod were investigated. Na-iccuznsod transcription levels showed a general tendency of an initial up-regulation followed by a down-regulation in liver, gill, and head-kidney when yellow drum were exposed to ammonia-N/nitrite-N at the lethal concentration 50 at 96 h post-treatment, suggesting the important role of Na-icCuZnSOD in eliminating reactive oxygen species (ROS) induced by ammonia-N/nitrite-N. In addition, the characteristics of Na-icCuZnSOD protein and its comparative analysis with Na-ecCuZnSOD were investigated. Na-icCuZnSOD protein showed high enzyme stabilities over a wide range of temperature (10 to 60 °C) and pH (4.9 to 11.0), indicating its broad in vitro applications in many industries. Furthermore, the comparative analysis of Na-icCuZnSOD and Na-ecCuZnSOD gives a new perspective for the study of their structure-function relationship. Collectively, the present study will advance our understanding of the toxicity of ammonia-N/nitrite-N on yellow drum through testing the mRNA expression of iccuznsod gene, and broaden our knowledge of the protein characteristics of icCuZnSOD from fish.