Purification and characterization of a psychrophilic catalase from Antarctic Bacillus

• Published in: Canadian Journal of Microbiology
• Main Authors: Wang, Wei, Sun, Mi, Liu, Wanshun, Zhang, Bin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2008
• Subjects: Antarctic; Antarc*
• Online Access: http://dx.doi.org/10.1139/w08-066; http://www.nrcresearchpress.com/doi/full-xml/10.1139/W08-066; http://www.nrcresearchpress.com/doi/pdf/10.1139/W08-066

Catalase from Bacillus sp. N2a (BNC) isolated from Antarctic seawater was purified to homogeneity. BNC has a molecular mass of about 230 kDa and is composed of four identical subunits of 56 kDa. The catalase showed optimal activity at 25 °C and at a pH range of 6–11. The enzyme could be inhibited by azide, hydroxylamine, and mercaptoethanol. These characteristics suggested that BNC is a small-subunit monofunctional catalase. The activation energy of BNC was 13 kJ/mol and the apparent k cat /K m values were 3.6 × 10 6 and 4 × 10 6 L·mol –1 ·s –1 at 4 and 25 °C, respectively. High catalytic efficiency of BNC at low temperatures enables this bacterium to scavenge H 2 O 2 efficiently. BNC exhibited activation energy, catalytic efficiency, and thermostability comparable with some mesophilic homologues. Such similarity of enzymatic characteristics to mesophilic homologues, although uncommon among the cold-adapted enzymes in general, has also been observed in other psychrophilic small-subunit monofunctional catalases.