RT Journal Article SR Electronic(1) A1 Loprasert, Suvit A1 Negoro, Seiji A1 Okada, HirosukeYR 1988 T1 Thermostable Peroxidase from Bacillus stearothermophilus JF Microbiology, VO 134 IS 7 SP 1971 OP 1976 DO https://doi.org/10.1099/00221287-134-7-1971 PB Microbiology Society, SN 1465-2080, AB A peroxidase from Bacillus stearothermophilus was purified to homogeneity. The enzyme (M r 175000) was composed of two subunits of equal size, and showed a Soret band at 406 nm. On reduction with sodium dithionite, absorption at 434 nm and 558 nm was observed. The spectrum of reduced pyridine haemochrome showed peaks at 418, 526 and 557 nm; the reduced minus oxidized spectrum of pyridine haemochrome showed peaks of 418, 524 and 556 nm with a trough at 452 nm. These results indicate that the enzyme contained protohaem IX as a prosthetic group. The optimum pH was about 6 and the apparent optimum temperature was 70 °C. The enzyme was relatively stable up to 70 °C; at 30 °C it was stable for a month. The enzyme had peroxidase activity toward a mixture of 2,4-dichlorophenol and 4-aminoantipyrine with a K m for H2O2 of 1·3 mm. It also acted as a catalase with a K m for H2O2 of 7·5 mm., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-134-7-1971