Isomaltase () is an enzyme that breaks the bonds linking saccharides, which cannot be broken by amylase or maltase. It digests polysaccharides at the alpha 1-6 linkages. Its substrate, alpha-limit dextrin, is a product of amylopectin digestion that retains its 1-6 linkage (its alpha 1-4 linkages having already been broken down by amylase). The product of the enzymatic digestion of alpha-limit dextrin by isomaltase is maltose. Isomaltase helps amylase to digest alpha-limit dextrin to produce maltose. The human sucrase-isomaltase is a dual-function enzyme with two GH31 domains, one serving as the isomaltase, the other as a sucrose alpha-glucosidase. Nomenclature The systematic name of sucrase-isomaltase is oligosaccharide 6-alpha-glucohydrolase. This enzyme is also known as: Sucrase-alpha-dextrinase oligo-1,6-glucosidase, limit dextrin, so maltase, exo-oligo-1,6-glucosidase, dextrin 6alpha-glucanohydrolase, alpha-limit dextrin, dextrin 6-glucanohydrolase, and oligosaccharide alpha-1,6-glucohydrolase. Mechanism This enzyme catalyses the following chemical reaction Hydrolysis of (1->6)-alpha-D-glucosidic linkages in some oligosaccharides produced from starch and glycogen by enzyme EC 3.2.1.1. Hydrolysis uses water to cleave chemical bonds. Sucrase-isomaltase’s mechanism results in a net retention of configuration at the anomeric center. External links References Hydrolases