β -galactosidase was extracted from apricots ( Prunus armeniaca kaisa ) and characterized biochemically. Three isoenzymes ( β -gal I, β -gal II and β -gal III) were obtained by salt fractionation and ionexchange and Sephadex G-100 column chromatography. β -galactosidase II showed a high ability to hy-drolyze the substrate p-nitrophenyl β -D-galactopyranoside than that of β -galactosidase I and III. The individual peaks showed charge homogeneity as revealed by single band on polyacrylamide gel. The molecular weight of β -gal I, β -gal II and β -gal III as determined by gel filtration was found to be 44.15, 34.70 and 23.71 KDa respectively. The optimum pH for the activity different isozymes was found between 4 and 6. The isoenzymes were determined to be thermally stable upto 40?C. The Km value for β -gal I was 1.85 mM which was higher than that of β -gal II (K m = 1.7), and β -gal III (K m = 1.19). The V max value for β -gal I, β -gal II and β -gal III was found to be 0.52, 0.70 and 0.38 μmole/min respectively.
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