Abstract
An α-glucosidase which was homogeneous in disc electrophoretic and ultracentrifugal analysis was obtained from buckwheat seeds by fractionation with ammonium sulfate, chromatography on CM-cellulose and gel filtration on Bio-Gel P-150. The sedimentation coefficient (S20, w) was estimated to be 6.2 S, and the molecular weight, 80, 000_??_88, 000. The ratio of initial velocity of hydrolysis for maltose (Km=2.13mg/ml) and soluble starch (Km=7.46mg/ml) was calculated to be 100:86. Both activities were competitively inhibited by Tris and erythritol, and stimulated approximately 1.5-fold in the presence of 25mM-K+ or Na+. The Ki values for Tris on hydrolysis of maltose and soluble starch were 0.78mM and 1.07mM, and those for erythritol, 77.7mM and 64mM, respectively.
