Conditions required to stabilize ß-galactosidase activity in apple extracts were found. ß-Galactosidase was most stable at neutral pH and in the presence of certain additives, in particular PVP and CETAB, which were used in the purification. Most of the glycosidase activities present in the apple were effectively extracted with 50 mmol/L phosphate buffer pH 7.0. The purification procedure consisted of acetone powder preparation to remove polyphenols, ammonium sulphate fractionation, ion-exchange and high performance liquid chromatographic (HPLC) techniques. Nine glycosidase activities were detected in the acetone powder preparation of the apple cortex by fluorometric assay using 4-methylumbelliferyl glycosides as substrates. A major contaminant, polyphenoloxidase, was removed by the anion exchange chromatography. The major B-galactosidase fraction also contained ß-fucosidase and α-L-arabinosidase activities. These three activities were found in a single protein peak (M.W. 77,600) in the HPLC. While the purification indicated a single enzyme species, kinetic analysis indicated separate but interacting active sites for each substrate. Mixed substrate kinetic analysis showed activation of hydrolysis of one substrate by another. Also, methyl-ß-D-galactopyranoside and D-galactonic acid-Y-lactone were competitive inhibitors of the ß-galactosidase but non-competitive inhibitors of both the α-L-arabinosidase and ß-fucosidase. All the glycosidases had optimal activities in the pH range of 4-5 and different Kₘ values. They were all inhibited by rutin, quercetin and chlorogenic acid but to different extents.