Purification and properties of Aerococcus viridans lactate oxidase

Lactate oxidase was purified from cells of Aerococcus viridans by a procedure which utilized ammonium sulfate fractionation, DEAE Sepharose CL-6B chromatography, and Sephadex G-100 chromatography. The final preparation was homogeneous by SDS-polyacrylamide gel electrophoresis. The enzyme appears to be a tetramer with a subunit molecular weight of 44,000 and utilizes FMN as a cofactor. The enzyme was highly specific for L-lactate. D-lactate, glycolate, and D,L-2-hydroxybutyrate were not oxidized by the enzyme but were competitive inhibitors. The enzyme could be irreversibly inactivated by incubation with bromopyruvate. This inactivation appears to involve a covalent modification near the active site of the enzyme; however, the flavin cofactor is not the site of this modification.