Abstract ▼ AI-Helper

Deinococcus radiodurans (D. radiodurans) shows remarkable resistance to reactive oxygen species (ROS), generated by ionizing radiation. The mechanisms involved in the response of these bacteria to ROS are poorly understood. Catalase plays a key role in protecting cells against ROS. In the present st...

Deinococcus radiodurans (D. radiodurans) shows remarkable resistance to reactive oxygen species (ROS), generated by ionizing radiation. The mechanisms involved in the response of these bacteria to ROS are poorly understood. Catalase plays a key role in protecting cells against ROS. In the present study reports the cloning, purification and characterization of catalases from the highly radioresistant bacterium D. radiodurans. D. radiodurans had three types {KatA, KatP (unknown) and KatE} of catalase which were expressed in each growth period. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of the purified D. radiodurans KatA showed a molecular weight of 60.4 kDa. KatA exhibited an apparent Km value of 10.9 mM and a Vmax of 1.475 mM·min^(-1). The activity of KatA was higher in alkali pH and highest at 30℃. The activity of KatA was inhibited by sodium azide (NaN₃), sodium cyanide (NaCN) and hydroxylamine (NH₂OH) and the absorption spectrum of KatA showed a soret band at 406 nm. Molecular weight of KatE was approximately 83 kDa determined by SDS-PAGE. KatE exhibited an apparent Km value of 28.3 mM and a Vmax of 6.757 mM·min^(-1). An optimum pH and temperature for KatE activity were pH 7 and 30℃, respectively. The catalase activity of KatE was inhibited by N_(a)N_(3), N_(a)CN and NH_(2)OH and the absorption spectrum showed a soret band at 412 nm. This study suggests that consistent expression of three catalases in D. radiodurans which includes KatA and KatE contribute to its extreme resistance to radiation.

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