A manganese catalase from Thermomicrobium roseum with peroxidase and catecholase activity

An enzyme with catechol oxidase activity was identified in Thermomicrobium roseum extracts via solution assays and activity-stained SDS-PAGE. Yet, the genome of T. roseum does not harbor a catecholase gene. The enzyme was purified with two anion exchange chromatography steps and ultimately identified to be a manganese catalase with additional peroxidase and catecholase activity. Catalase activity (6280 +/- 430 IU/mg) clearly dominated over pyrogallol peroxidase (231 +/- 53 IU/mg) and catecholase (3.07 +/- 0.56 IU/mg) activity as determined at 70 A degrees C. Most enzyme kinetic properties were comparable to previously characterized manganese catalase enzymes. Catalase activity was highest at alkaline pH values and showed inhibition by excess substrate and chloride. The apparent K (m) and k (cat) values were 20 mM and 2.02 x 10(4) s(-1) subunit(-1) at 25 A degrees C and pH 7.0.