α-GALACTOSIDASE OF ASPERGILLUS NIGER: PURIFICATION AND PROPERTIES

Highly purified α-galactosidase (specific activiys 25 U/mg protein) has been isolated from the cultural liquid of Aspergillus niger. The enzyme is thermo- and pH-stable, with pH-optimum 4.1, and temperature optimum 60 °C. Km and Vmax for nitrophenyl substrate was shown to be 1.19 mM and 25 µmol/min/mg protein, respectively. α-Galactosidase was inhibited by the product of reaction D-galactose (Ki – 6.2 × 10-2M). The enzyme displayed narrow specificity towards glycon. It proved to be metal-independent. The active center of the enzyme contains the carboxylic group of the C-terminal aminoacid and imidazole group of histidine.