Alpha-glucosidase with broad substrate specificity for alpha-1,4- and alpha-1,6-glucosides. Not required for isomaltose utilization, but overexpression allows the IMA1 null mutant to grow on isomaltose. Hydrolysis of (1->6)-alpha-D-glucosidic linkages in some oligosaccharides produced from starch and glycogen by alpha-amylase, and in isomaltose. Belongs to the glycosyl hydrolase 13 family.