Multiple forms of intracellular alpha-glucosidase from Thermoascus aurantiacus Miehe: purification and properties

The intracellular alpha-glucosidase extracted from the mycelium of Thermoascus aurantiacus was resolved by chromatographic procedures on DEAE-cellulose and hydroxylapatite into 4 major forms which account for 96% of the recovered activity. These forms, purified to electrophoretic homogeneity, display the same affinity toward p-nitrophenyl-alpha-glucoside (Km = 0.24 mM at pH 4 and 70 degrees C), the same molecular weight on Sephadex G-200 (140,000-145,000) and isoelectric point (4.2) and are protected by Cl- and H+ ions from heat denaturation at 70 degrees C. They differ in the carbohydrate content which varies between 14 and 31%, w/w.