Purification and Some Properties of Acid Invertase of Persimmon Fruits

抄録

Single cells were prepared from mesocarp tissue of ripe persimmon (Diospyros kaki cv.Fuyu) fruits, and inter-or intracellular localization of acid invertase (AI, EC 3.2.1.26) was studied. AI was localized in the intercellular fraction (cell wall fraction). AI was isolated and purified from the cell wall fraction of ripe persimmon fruits by column chromatography on SE-53 cellulose and Toyopearl HW 55F. The specific activity of purified AI was 570 units per mg protein at 30°C. The molecular mass of AI was estimated to be 44 kDa by gel filtration over Sephacryl S-200 and 70 kDa by SDS-PAGE. The optimum pH of the activity for sucrose was 4.25. The purified enzyme hydrolyzed sucrose and raffinose but not melibiose. The enzyme had a K_m of 3.2 mM for sucrose and a K_m of 2.6 mM for raffinose. Silver nitrate (5μM), HgCl₂ (2μM), p-chloromercuribenzoate (100 mM), pyridoxamine (10mM), and pyridoxine (2.5 mM) inhibited AI activity by 95, 85, 100, 41, and 30%, respectively.