Multiple forms of neutral α-glucosidase (pH optima, 6.0~6.5) were purified from pig duodenal mucosa by a procedure including Triton X-100 treatment, fractionation with ammonium sulfate, fractionation with ethyl alcohol, DEAE-cellulose column chromatography and preparative polyacrylamide disc gel electrophoresis. All of the α-glucosidases, Ia, IIa, Ib and IIb, were found to be homogeneous on polyacrylamide disc gel electrophoresis. The molecular weights, isoelectric points and optimum temperatures of α-glueosidases Ia and IIa were 145,000~150,000, pH 3.5~3.7 and 55°C, respectively, and both enzymes were stable up to 55°C on treatment at pH 6.0 for 15 min; whereas those of the other two α-glucosidases, Ib and IIb, were 80,000, pH 4.0~4.1 and 65°C, respectively, and both enzymes were stable up to 70°C on the same treatment. The Km values of enzyme IIa for maltose, maltotriose and amylose were 1.72mm, 0.37 mm and 1.67mg/ml, while those of enzyme IIb were 3.33 mm, 2.61 mm and 11.8 mg/ml, respectively. All enzy...