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Purification and characterization of a psychrophilic catalase from Antarctic Bacillus

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Abstract:

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 kcat/Km values were 3.6 × 106 and 4 × 106 L·mol-1·s-1 at 4 and 25 °C, respectively. High catalytic efficiency of BNC at low temperatures enables this bacterium to scavenge H2O2 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.

La catalase de Bacillus sp. N2a (BNC) isolée des eaux de l’Antarctique a été purifiée à homogénéité. La BNC a une masse moléculaire d’environ 230 kDa et elle est composée de quatre sous-unités identiques de 56 kDa. La catalase démontrait une activité maximale à 25  °C et dans une gamme de pH de 6 à 11. L’enzyme pouvait être inhibée par l’azide, l’hydroxylamine et le mercaptoéthanol. Ces caractéristiques suggèrent que la BNC soit une catalase monofonctionnelle à petites sous-unités. L’énergie d’activation de la BNC était de 13 kJ/mol et le kcat/Km apparent était de 3,6 × 106 et 4 × 106 L·mol-1·s-1 à 4 et 25  °C, respectivement. Le haut rendement catalytique de la BNC à basse température permet à cette bactérie de piéger efficacement le H2O2. La BNC montrait une énergie d’activation, un rendement catalytique et une thermostabilité comparable à celles d’homologues mésophiles. Une telle similarité des caractéristiques enzymatiques avec celles d’homologues mésophiles, quoique peu commune chez les enzymes adaptées au froid en général, a aussi été observée chez d’autres catalases monofonctionnelles à petites sous-unités des psychrophiles.

Document Type: Research Article

Publication date: October 1, 2008

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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