Isomaltase
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. 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 dextrine,
- so maltase,
- exo-oligo-1,6-glucosidase,
- dextrin 6alpha-glucanohydrolase,
- alpha-limit dextrine,
- dextrin 6-glucanohydrolase, and
- oligosaccharide alpha-1,6-glucohydrolase.
Mechanism
This enzyme catalyses the following chemical reaction
Hydrolysis uses water to cleave chemical bonds. Sucrase-isomaltase’s mechanism results in a net retention of configuration at the anomeric center.
