Cloning, characterization and tissue expression of disk abalone ( Haliotis discus discus) catalase

Abstract

Catalase is an antioxidant enzyme that plays a significant role in protection against oxidative stress by detoxification of hydrogen peroxide (H 2O 2). A gene coding for a putative catalase was isolated from the disk abalone ( Haliotis discus discus) cDNA library and denoted as Ab-catalase. The full-length (2864 bp) Ab-catalase cDNA contained 1,503 bp open reading frame (ORF), encoding 501 amino acid residues with 56 kDa predicted molecular weight. The deduced amino acid sequence of Ab-catalase has characteristic features of catalase family such as catalytic site motif ( 61FNRERIPERVVHAKGAG 77), heme-ligand signature motif ( 351RLYSYSDT 358), NADPH and heme binding residues. Phylogenetic and pairwise identity results indicated that Ab-catalase is more similar to scallop ( Chlamys farreri) catalase with 80% amino acid identity except for other reported disk abalone catalase sequences. Constitutive Ab-catalase expression was detected in gill, mantle, gonad, hemocytes, abductor muscle and digestive tract in tissue specific manner. Ab-catalase mRNA was up-regulated in gill and digestive tract tissues for the first 3 h post injection of H 2O 2, showing the inducible ability of abalone catalase against oxidative stress generated by H 2O 2. The purified recombinant catalase showed 30,000 U/mg enzymatic activity against H 2O 2 and biochemical properties of higher thermal stability and broad spectrum of pH. Our results suggest that abalone catalase may play an important role in regulating oxidative stress by scavenging H 2O 2.