A 2 804 bp full-length cDNA sequence of catalase(CAT)gene from Hypriopsis cumingii was obtained by rapid amplification of cDNA ends.It consists of a 112 bp 5′UTR(untranslated region),a 1 388 bp ORF(open reading frame)and a 1 303 bp 3′UTR,and the deduced protein is composed of 462 amino acids,with calculated molecular weight of 52.7 ku,and its isoelectric point was 6.35.Motif analysis showed that CAT deduced amino acid sequence contained a highly conserved catalytic site motif “23FDRERIPERVVHAKGAG39”.Twelve amino acids(Asp107,His153,Phe157,Ser160,Arg162,Asn172,Try174,Lys196,Val261,Trp262,His264 and Try317)of CAT gene of H.cumingii were identified as putative residues involved in NADPH binding,and they were different in different species.The CAT amino acid residues of H.cumingii shared a high similarity with other molluscs(99%),and shrimp,fish,amphibians,mammals(98%-99%).The obtained CAT of H.cumingii was predicted as CAT3.NJ tree suggested that H.cumingii clustered with mollusca firstly,and then clustered with shrimp,fish,amphibians and mammals.Real-time quantitative RT-PCR results displayed that CAT gene was expressed in a wide range of seven organs,with the lowest level of transcripts found in kidney.Its expression was upregulated in blood,which was significantly different from other organs.The expressions of other five organs were generally upregulated first and then downregulated.