Isomaltase (EC 188.8.131.52) 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.
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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.
The systematic name of sucrase-isomaltase is oligosaccharide 6-alpha-glucohydrolase. This enzyme is also known as:
- limit dextrin,
- so maltase,
- dextrin 6alpha-glucanohydrolase,
- alpha-limit dextrin,
- dextrin 6-glucanohydrolase, and
- oligosaccharide alpha-1,6-glucohydrolase.
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 184.108.40.206.
Hydrolysis uses water to cleave chemical bonds. Sucrase-isomaltase’s mechanism results in a net retention of configuration at the anomeric center.
- Isomaltase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
- ^ Sim L, Willemsma C, Mohan S, Naim HY, Pinto BM, Rose DR (June 2010). "Structural basis for substrate selectivity in human maltase-glucoamylase and sucrase-isomaltase N-terminal domains". The Journal of Biological Chemistry. 285 (23): 17763–70. doi:10.1074/jbc.M109.078980. PMC 2878540. PMID 20356844.