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Purification and Characterization of a ß-Galactosidase from Fusarium oxysporum var. lini

Departamento Bioquímica-Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Caixa Postal 2486, 30.161 - Belo Horizonte - MG, Brazil

ABSTRACT

ß-D-Galactosidase was purified from a cellular extract of Fusarium oxysporum var. lini by heat shock and successive chromatography on DEAE-cellulose DE-52 and Sephadex G-100. The purified enzyme was homogeneous on SDS gel electrophoresis. It was inhibited by divalent cations such as Zn⁺⁺, Mg⁺⁺, and Ca⁺⁺. The Michaelis constant and maximum velocity values for o-nitrophenyl ß-D-galacto-pyranoside were 6.76 mM and 816.7 µmol·mg protein^–1·^–1. The isoelectric point was 3.83, and the optimal pH and temperature were 5.0 and 55°C. The estimated molecular weight of the enzyme was 224,000 by gel filtration and 36,300 by SDS-PAGE. The enzyme was considered a hexamer. o-Nitrophenyl-ß-D-galacto-pyranoside hydrolysis was activated by lactose, suggesting an allosteric nature of the enzyme.