1990 Volume 37 Issue 4 Pages 298-305
β-D-Galactosidase was purified from kiwifruit by ammonium sulfate fractionationfollowed by series of column chromatography on DEAE-cellulose, CM-cellulose, hydroxylapatite, Sepharose 2B, and Sephadex G-150. The purified enzyme was found to be homogeneous by polyacrylamide gel electrophoresis. The molecular weight of the enzyme was estimated to be 145000 by gel filtration, and the optimum pH was 3.5. The enzyme was relatively stable in the pH range of 3.5-5.0 and up to 37°C during 10min incubations. The Km values for p-nitrophenyl β-D-galactoside, lactose and lactulose were 0.6mM, 5.3mM and 6.7mM, respectively. Inhibition was observed at higher concentrations of these substrates. The effects of various compounds on the enzyme activity including metal ions, SH-reagents and sugars were investigated. The enzyme was inhibited by Hg2+ and 0.1mM p-chloromercuribenzoate. The other compounds had no significant effects on the activity.
