A novel thermo-alkali stable catalase–peroxidase from Oceanobacillus oncorhynchi subsp. incaldaniensis: purification and characterization

A novel thermo-alkali-stable catalase–peroxidase from Oceanobacillus oncorhynchi subsp. incaldaniensis subsp. nov., strain 20AG, was purified and characterized. The protein purified from the cells resulted in 110-fold purification with a specific activity of 35,000 U/mg. The enzyme consisted of four identical subunits of 72 kDa as determined by SDS-PAGE and the total molecular mass measured by gel filtration was 280 kDa. The heme content was determined to be 1 heme per homodimer. The enzyme showed a Soret peak at 406 nm in the oxidized form and was easily reduced by dithionite. The enzyme showed an appreciable peroxidase activity in addition to high catalase activity. The behaviour of this heme-enzyme was typical of the class of prokaryotic catalase–peroxidases, which are sensitive to cyanide and insensitive to the eukaryotic catalase inhibitor 3-amino-1,2,4-triazole. The enzyme was active over a temperature range from 30 to 60°C and a pH range from 5 to 10, with an optimum pH about 9.0 and an optimum temperature of 40°C. The enzyme was stable in the pH range of 5.0 to 10.0 after 1 h of treatment at 40°C. The enzyme was stable for 24 h at 40°C with a half-life of 4 h 60°C. The enzyme had a K _m of 24 mM for hydrogen peroxide. The amino terminal amino acid sequence of the catalase–peroxidase from strain 20AG was SEKRKMTTAFGA and it showed no homology with other catalases.