Beta-D-galactosidase and alpha-L-arabinofuranosidase activities during the softening of apples

Four β-D-galactosidases (GA-ase I, II, III, and IV) and one α-L-arabinofuranosidase (AF-ase) activities were detected in cell wall extracts from apples (Mains dornestica Borkh. cv. Starking Delicious) stored at 0°C for five months.The GA-ase fractions separated by hydroxylapatite column chromatography degraded a polyuronide prepared from apple cell walls, releasing galactose. GA-ase II, III, and IV fractions contained arabinogalactan degrading and galactose releasing activities, but GA- ase I failed to degrade arabinogalactan. AF-ase fraction degraded polyuronide and arabinogalactan releasing arabinose and other sugars.The activities of GA-ase II, III and IV decreased gradually as the apples softened in storage. The activities of GA-ase I and AF-ase which were not detectable at harvest, appeared and increased during storage.These galactose and arabinose releasing activities, may be involved in the degradation and solubilization of polyuronide, araban, and galactan in the cell walls of apples during softening.