α-Glucosidase (α-D-glucoside glucohydrolase EC 3.2.1.20) was purified approximately 30-fold from grape berries (Vitis vinifera var. Riesling). Besides maltose the enzyme preparation hydrolyzes to a lesser extent maltotriose, isomaltose, and starch. It has a pH optimum of 5.1 and a molecular weight