PURIFICATION AND SUBSTRATE-SPECIFICITY OF ALPHA-GLUCOSIDASE FROM PAECILOMYCES-VARIOTI AHU 9417

An extracellular alpha-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 hydrolyzed maltooligosaccharides and isomaltooligosaccharides. The ratios of V(max) for maltose, isomaltose, kojibiose, nigerose, phenyl alpha-glucoside, maltotriose, isomaltotriose, panose, phenyl alpha-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.