Biochemical properties of β-glucosidase from Turkish Hacıhaliloğlu apricot (Prunus armenica L.) as affected by harvest year

•Two isoenzymes (isoenzyme A and B) were obtained with purification.•The isoenzymes exhibited different kinetic properties.•Both the isoenzymes had a different affinity towards p-nitrophenyl-β-d-glucopyranoside.•The inactivation kinetics exhibited significant year-to-year variation.•CaCl2 was the most effective inhibitor for isoenzymes.

β-glucosidase was extracted and purified from Turkish Hacihaliloğlu apricot variety and some of its biochemical properties were studied in a two-year study (2008 and 2009). Two isoenzymes (isoenzyme A and B) were obtained upon ammonium sulfate fractionation, ion exchange chromatography using DEAE-Toyopearl 650 M and gel filtration chromatography using Sephadex G-100. The pH optimum was found to be 5.0 for both isoenzymes. The optimum temperature for isoenzyme A activity in both years was found to be 50 °C, whereas those for the isoenzyme B in 2008 and 2009 were 50 °C and 55 °C, respectively. Km values of the isoenzyme A and B were found to be 2.49 and 1.12 mM in 2008, and 2.41 and 1.06 mM in 2009, respectively. The Z values for isoenzyme A in 2008 and 2009 were found to be 20.3 °C and 17.9 °C, respectively. Those for isoenzyme B in 2008 and 2009 were 21.1 °C and 23.0 °C, respectively. Ea values for isoenzyme A were 108.1 kj/molK and 122.3 kj/molK, while those for isoenzyme B were found to be 103.5 kj/mol K and 95.1 kj/molK in 2008 and 2009, respectively. Of the inhibitors tested, CaCl2 was the most effective.