isomaltase
{{Infobox enzyme
|EC_number=3.2.1.10
|Name=Oligo-1,6-glucosidase
}}
Isomaltase ({{EC number|3.2.1.10}}) 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
File:Sucrase-Isomaltase Mechanism.png
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.{{cite journal | vauthors = Sim L, Willemsma C, Mohan S, Naim HY, Pinto BM, Rose DR | title = Structural basis for substrate selectivity in human maltase-glucoamylase and sucrase-isomaltase N-terminal domains | journal = The Journal of Biological Chemistry | volume = 285 | issue = 23 | pages = 17763–70 | date = June 2010 | pmid = 20356844 | pmc = 2878540 | doi = 10.1074/jbc.M109.078980 | doi-access = free }}
External links
- {{MeshName|Isomaltase}}