Isolation and characterization of the pseudocatalase of Lactobacillus plantarum.

The nonheme, or pseudo, catalase of Lactobacillus plantarum has been purified to homogeneity. This enzyme is pink in concentrated solutions and has a molecular weight of 172,000 +/- 4,000. It is composed of six noncovalently associated subunits of molecular weight 28,300 +/- 600. This pseudocatalase contains 1.12 +/- 0.37 atoms of manganese per subunit. Fe, Co, Cu, and Zn, if present at all, were at less than 0.1 atom per subunit. At pH 7.0 and at 25 degrees C the Km for H2O2 is 250 mM and the turnover number at Vm was 3.9 x 10(5) mol of H2O2 per mol of enzyme per s. The optical spectrum of pseudocatalase is similar to that of the manganese superoxide dismutase and indicates the presence of Mn(III) in the resting enzyme. Pseudocatalase does not exhibit superoxide dismutase activity nor does the manganese-containing superoxide dismutase exhibit catalase activity. This pseudocatalase is stable to freezing and thawing and lost only 40% of its activity when heated to 80 degrees C for 5 min. Strains of L. plantarum which contain pseudocatalase did not accumulate H2O2 in the growth medium.