Purification and characterization of catalase-2 from Deinococcus radiophilus

A bifunctional catalase-peroxidase, designated catalase-2, of a UV resistant Deinococcus radiophilus was purified to electrophoretic homogeneity by both chromatographic and electrophoretic methods. Its molecular weight was 310 kDa and composed of a tetramer of 80 kDa subunits. The catalase-2 exerted its optimal activity at 30 degrees C and around pH 9. Its K-m value for H2O2 was about 10 mM. It shelved the typical ferric heme spectrum with maximum absorption af 403 nm which shifted to 419 nm in the presence of cyanide. The ratio of A(403)/A(280) was 0.48. Fifty percent inhibition of the enzyme activity was observed at 4.6 x 10(-6), 7.7 x 10(-6), and 3.0 x 10(-7) M of NaCN, NaN3, and NH2OH, respectively. The enzyme was thermostable and not sensitive to 3-amino-1,2,4-triazole. Treatment of the enzyme with ethanol-chloroform caused a partial loss (30%) of its activity. The catalase-2 was distinct from the Deinococcal bifunctional catalase-3 in a number of properties, particularly in its molecular structure and substrate affinity.