Studies on α-Glucosidase in Rice

Two kinds of αglucosidase which were homogeneous in disc electrophoretic and ultra-centrifugal analysis were isolated from rice seeds by means of ammonium sulfate fractionation and CM-cellulose, Sephadex G–100 and DEAE-cellulose column chromatography and designated as α-glucosidase I and α-glucosidase II. Both α-glucosidases hydrolyzed maltose and soluble starch to glucose and showed same optimal pH (4.0) on the both substrates. In addition, both enzymes acted on various α-linked gluco-oligosaccharides and soluble starch but little or not on α-linked hetero-glucosides and α-l,6-glucan (dextran). Activity of the enzymes on maltose and soluble starch was inhibited by Tris and erythritol. α-Glucosidase II was more sensitive to the inhibitors than α-glucosidase I. Km value for maltose was 1.1 mM for α-glucosidase I and 2.0 mM for α-glucosidase II.