Molecular Cloning and Characteristics of Catalase cDNA from Chinese Soft-shelled Turtle(Pelodiscus sinensis)

A catalase cDNA was cloned from the liver of the Chinese soft-shelled turtle(Pelodiscus sinensis) using reverse transcription-polymerase chain reaction(RT-PCR) with degenerate primers. Both 3'-and 5'-untranslated regions were isolated by the rapid amplification of cDNA ends method(RACE). Analysis of nucleotide sequence revealed that the catalase cDNA clone consisted of 2173 bp with an open reading frame of 1587 bp encoding a protein of 528 amino acids. The calculated molecular mass of the mature protein is 59.8 kDa with an estimated pI of 6.84. The peroxisomal targeting signal SNL at the C-terminal and two putative N-glycosylation sites NLSV and NVSQ were found in the catalase. Sequence comparison showed that this catalase, deduced by the amino acid sequence, had high similarity and identity with those of vertebrates recorded in GenBank. Four functional domains and conserved amino acids responsible for binding heme and NAPDH including four essential residues were observed. The 3-D homology model of the turtle catalase was predicted by SwissModel based on the relative domains of bovine catalase structure(PDB ID: 3rgp). The mRNA expression and enzyme activities in liver, brain, spleen, kidney, heart, gut, lung and muscle were investigated, and the results showed that the mRNA and enzyme activities of catalase in these tissues were species-specific.