Two forms of .ALPHA.-glucosidase from rice seeds at the milky stage.

Abstract

Two forms of α-glucosidase were isolated from rice seeds at the milky stage by a procedure that included fractionation with ammonium sulfate, DEAE-cellulose column chromatography, CM-cellulose column chromatography, SP-Sephadex column chromatography and preparative disc gel electrophoresis. The isolated α-glucosidases were designated as α-glucosidase I and α-glucosidase II, and were glycoproteins containing 5.5% and 3.4% carbohydrate, respectively. The molecular weight and isoelectric point were: 78,900 and pH 9.3 for α-glucosidase I, and 47,300 and pH 9.3 for α-glucosidase II. They were found to be homogeneous on polyacrylamide disc gel electrophoresis. The two enzymes hydrolyzed maltose, maltotriose, phenyl α-maltoside, amylose and soluble starch to liberate glucose, but did not act on sucrose. Their enzymes produced maltotriose and 4-α-nigerosyl-glucose from maltose as main α-glucosyltransfer products. They hydrolyzed amylose to liberate α-glucose.