IDENTIFICATION AND CHARACTERIZATION OF THE CATALASE GENE Py CAT FROM THE RED ALGA PYROPIA YEZOENSIS (BANGIALES, RHODOPHYTA) 1

Catalase is an antioxidant enzyme that plays a significant role in protection against oxidative stress by reducing hydrogen peroxide. The full‐length catalase cDNA sequence as isolated from expressed sequence tags (ESTs) of Pyropia yezoensis (Ueda) M. S. Hwang et H. G. Choi ( Py CAT) through rapid amplification of cDNA ends (RACE) was identified and characterized. It encoded a polypeptide of 529 amino acids, which shared 36%–44% similarity with other known catalase proteins. Phylogenetic analysis revealed that Py CAT was closer to the catalases from plants than from other organisms. The Py CAT mRNA expression was investigated using real‐time PCR to determine life‐cycle‐specific expression and the expression pattern during desiccation. The mRNA expression level in gametophytes was significantly higher than in sporophytes, and the mRNA expression level of Py CAT was significantly up‐regulated during the desiccation process. The recombinant Py CAT protein was purified and analyzed biochemically. The recombinant Py CAT protein exhibited high enzymatic activity (28,000 U·mg −1 ) with high thermal stability and a broad pH range. All these results indicate that the Py CAT is a typical member of the plant and algal catalase family and may play a significant role in minimizing the effect of oxidative damage in P. yezoensis during desiccation.