Kinetic Studies on β -Galactosidase Isolated from Apricots ( Prunus armeniaca kaisa)

Abstract

β-galactosidase was extracted from apricots (Prunus armeniaca kaisa) and characterized biochemically. Three isoen-zymes (β-gal I, β-gal II and β-gal III) were obtained by salt fractionation and ion-exchange and Sephadex G-100 column chromatography. β-galactosidase II showed a high ability to hydrolyze 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 up to 40˚C. The K m 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.