Disk Abalone, Haliotis discus discus , CuZn–Superoxide Dismutase cDNA and its Transcriptional Induction by Aroclor 1254

CuZn–superoxide dismutase (CuZn–SOD) is a key antioxidant enzyme playing a first line protective role against reactive oxygen species (ROS) by converting superoxide () into H 2 O 2 . The CuZn–SOD gene was isolated from a whole abalone cDNA library and denoted as aCuZn–SOD. The full‐length cDNA of aCuZn–SOD was 1021 bp, which contained 465‐bp open reading frame (ORF) coding 154 amino acids. It contained highly conserved CuZn–SOD signature motif 1 ( 45 GFHVHQFGDNT 55 ) and motif 2 ( 139 GNAGGRQACGVI 150 ). Also, amino acid residues identified as Cu (His 47 , His 49 , His 64 , and His 121 ) and Zn (His 64 , His 72 , His 81 , and ASP 84 ) metal‐binding sites were completely conserved in the aCuZn–SOD. The reverse transcription polymerase chain reaction (RT‐PCR) results showed that aCuZn–SOD mRNA was expressed constitutively in gill, mantle, gonad, abductor muscle, digestive tract, and hemocytes in a tissue‐specific manner. The aCuZn–SOD mRNA was significantly up‐regulated ( P < 0.05) in gill and digestive tract tissues after Aroclor 1254 induction compared to untreated and methanol‐injected abalone groups, suggesting that abalone has a potential use in assessing the impact of marine pollutants with the application of gene expression concept. In addition, purified recombinant aCuZn–SOD fusion protein was shown to reduce radical generated by xanthine oxidase assay, showing CuZn–SOD is a functionally active antioxidant enzyme in disk abalone.