Purification and characterisation of a β-glucosidase abundantly expressed in ripe sweet cherry ( Prunus avium L.) fruit

A β-glucosidase ( β- d-glucoside glucohydrolase, EC 3.2.1.21) was purified to homogeneity from ripe fruits of sweet cherry ( Prunus avium L.) by ammonium sulphate precipitation, ion exchange and size exclusion chromatography. The enzyme is a monomer with a molecular mass of ∼68 kDa and an acidic isoelectric point. N-terminal sequence analysis indicated that sweet cherry β-glucosidase is related to other plant cyanogenic β-glucosidases. Substrate specificity studies revealed that the enzyme is able to attack and hydrolyse several synthetic substrates and total cell walls purified from ripe fruit. Biochemical and immunolocalisation studies showed that sweet cherry β-glucosidases are mainly localised in the cytosol and in the apoplast, at the unripe stage of ripening; in ripe fruit it is also associated with cell wall.