Two extracellular proteins with alkaline peroxidase activity, a novel cytochrome c and a catalase-peroxidase, from Bacillus sp. No.13

Abstract

A novel cytochrome c and a catalase-peroxidase with alkaline peroxidase activity were purified from the culture supernatant of Bacillus sp. No.13 and characterized. The cytochrome c exhibited absorption maxima at 408 nm (Soret band) in its oxidized state, and 550 (α-band), 521 (β-band), and 415 (Soret band) nm in its reduced state. The native cytochrome c with a relative molecular mass of 15,000 was composed of two identical subunits. The cytochrome c showed over 50 times higher peroxidase activity than those of known c-type cytochromes from various sources. The optimum pH and temperature of the peroxidase activity were about 10.0 and 70 °C, respectively. The peroxidase activity is stable in the pH range of 6.0 to 10.8 (30 °C, 1-h treatment), and at temperatures up to 80 °C (pH 8.5, 20-min treatment). The heme content was determined to be 1 heme per subunit. The amino acid sequence of the cytochrome c showed high homology with those of the c-type cytochromes from Bacillus subtilis and Bacillus sp. PS3. The catalase-peroxidase showed high catalase activity and considerable peroxidase activity, the specific activities being 55,000 and 0.94 μmol/min/mg, respectively. The optimum pH and temperature of the peroxidase activity were in the range of 6.4 to 10.1 and 60 °C, respectively. The catalase-peroxidase showed a lower K m value (0.67 mM) as to H 2O 2 than known catalase-peroxidases.