Rapid Purfication of β -Galactosidase (Aspergillus Niger) from a Commercial Preparation

β-Galactosidase (A. niger) was purified from a commercial source in order to study the protein nature of the enzyme and some of its kinetic properties. The enzyme was rapidly purified by acetone precipitation, gel filtratior, and affinity chromatography. The specific activity of the purified enzyme was twice as high as that found in previous studies. The K_m and V_max for o-nitrophenyl β-D-galactopyranoside were 2.02 mM and 345 μmoles/min/mg protein respectively at pH 4.5 and 37°C. The procedure described yields a highly active enzyme which may be suitable for immobilization and hydrolysis of lactose. The molecular weight of the enzyme was 117,000 and the isolectric point was 4.9. The enzyme appears to be a glycoprotein and may contain multiple molecular forms.