Purification and Substrate Specificity of α-Glucosidase from Paecilomyces varioti AHU 9417

An extracellular α-glucosidase was purified from the culture broth of Paecilomyces varioti AHU 9417 by a combination of precipitation with ethanol, chromatography on DEAE-Sepharose CL-6B and Bio-Gel P-150, and preparative gel electrophoresis. The enzyme migrated as a single band on polyacrylamide gel electrophoresis. The molecular weight was estimated to be 100,000 by SDS-disc electrophoresis, and the optimum pH of activity was 4.5. The enzyme had a wide substrate specificity, as it rapidly hydrolysed maltooligosaccharides and isomaltooligosaccharides. The ratios of V max for maltose, isomaltose, kojibiose, nigerose, phenyl α-glucoside, maltotriose, isomaltotriose, panose, phenyl α-maltoside, and soluble starch were estimated to be 100, 72, 31, 105, 9.6, 103, 73, 47, 115, and 66, and the K m (mM of nonreducing terminal) for these substrates were 0.40, 2.4, 1.6, 2.5, 0.23, 0.33, 4.6, 0.67, 0.24, and 4.7 mM, respectively. The enzyme is characterized by a high activity toward isomaltose.