Full-length cDNA Cloning, Sequence Homology Analysis and Tissue Expression of a Catalase Gene from Grass Carp (Ctenopharyngodon idellus)

Catalase (CAT) is a key enzyme in the antioxidant systems of living organisms and plays an important role in avoiding producing oxidative stress by eliminating hydrogen peroxide. In this paper, the full-length cDNA of CAT was cloned from hepatopancreas of grass carp ( Ctenopharyngodon idellus ). The full-lengthcDNA of CAT was 2 263 base-pairs (bp) (GenBank accession No. FJ560431), including a complete open reading frame (ORF) of 1 575 bp, a 5' untranslated region (UTR) of 118 bp and 3' UTR of 570 bp. The ORF encoded 525 amino acid (aa) residues and the molecular mass of the predicted protein was 59.59 kD with an estimated pI of 7.02. Near the termination codon of CAT cDNA of grass carp, the 3' UTR had a long and integrated AC repeat sequences, which had the same characteristic of catalase in zebrafish, silver carp and rodents. Sequence alignment results showed that the nucleotide sequence and the deduced amino acid sequence of grass carp CAT cDNA shared high identity with other selected species, about 93.4%~43.0% and 98.1%~63.3%, respectively. Meanwhile, the deduced amino acid sequence of CAT cDNA of grass carp had several highly conserved motifs compared with other animals, including the heme-ligand signal sequence “RLFSYPDTH”, the enzyme active center sequence “FDRERIPERVVHAKGA” and three catalytic amino acid residues (His 74 , Asn 147 and Tyr 357 ). Besides, the CAT of grass carp also had highly conserved heme binding pocket and NADPH binding site. According the above sequence characteristics, we can presume that the grass carp CAT gene belonged to the subgenotypes group of single-function or typical CAT gene in CAT family. Real-time quantitative PCR (Q-PCR) method was used to analyze the CAT mRNA expression characterization in 11 species of tissues in grass carp. The results showed that the expression of CAT mRNA was found in all the detected tissues, especially, strongly in hepatopancreas, followed by spleen, intestine, kidney, but poorly in muscle and lipid. Therefore, the results of this study would contribute to further investigate the genetic structure and function of fish CAT , and lay the foundation for CAT molecular mechanism of antioxidation.