Purification and dynamics property of #beta#-galactosidase isozyme of apple

Cell wall bound #beta#-galactosidase was extracted from apples (Malus pumila Mill. cv. Fuji), and four #beta#-galactosidase isozymes (GALase I, GALase II, GALase III and GALase IV) were separated with hydroxylapatite column chromatography. The degradation activities of GALase I and GALase II to the cell wall polysaccharide were very high, GALase I and GALase II may take part in the degradation of their cell wall polysaccharides and play an important role during softening of apple fruit, but the activities of GALase III and GALase IV were low; GALase I and GALase II were purified by the ion exchange chromatography using Mono Q, Mono S column and the gel chromatography using Superose 12HR column. Electrophoresis of purified GALase I and GALase II on a 10% SDS-polyacrylamide gel showed a single band with a molecular weight of about 80 kDa and 78 kDa respectively. The optimum pH value of GALase I and GALase II were about 4.5 and 4.2, and their K_(m) values were about 2.47 mmol/L and 1.11 mmol/L respectively.