Purification and characterization of two catalases from the entomopathogenic fungus Beauveria bassiana.

N. PEDRINI; R. CRESPO; MP. JUÁREZ

Cataratas del Iguazú, Misiones

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular.; 2004

Fungal catalases are a diverse group of enzymes with regard to their structure, function and cell localization. These tetrameric hemoproteins are classified in the ¡°small-subunit¡± and the ¡°large-subunit¡± groups. After purification to homogeneity by gel filtration and strong anion exchange chromatography, we found two different catalases in the entomopathogenic fungus Beauveria bassiana. The peroxisomal enzyme, involved in ¥â-oxidation reactions, showed a molecular mass of 54.7 kDa for each subunity. For the cytosolic form, a longer molecular mass (84 kDa) was estimated, exhibing a Soret peak at 406 nm in the absorption spectrum. Unlike the bifunctional catalase-peroxidases, and in coincidence with other fungal cytosolic catalases, this enzyme was not inhibited by high concentrations of substrate (hydrogen peroxide), with a Km value of 35 mM, and 92 % inhibition was detect after 10 min incubation with 3-amino-1,2,4-triazole. In addition, a broad range of optimal pH (6 to 11) and temperature (25 to 50 ¨¬C), with 35% activity remaining at 75 ¨¬C, were found. Present data showed the existence of two different catalases in B. bassiana, a peroxisomal form belonging to the small-subunit group and a monofunctional cytosolic form that belong to the large-subunit group.