Sucrase isomaltase
Sucrase isomaltase | ||
---|---|---|
Properties of human protein | ||
Mass / length primary structure | 1826 amino acids | |
Secondary to quaternary structure | single pass type 2 membrane protein | |
Identifier | ||
Gene name | SI | |
External IDs | ||
Enzyme classification | ||
EC, category | 3.2.1.10 , glycosidase | |
Response type | Hydrolysis of (1 → 6) -alpha-D-glucosidic bonds | |
Substrate | Limit dextrins, isomaltulose, isomaltotriose, panose | |
Products | longer maltosides, maltose, maltotriose, (ultimately) glucose | |
Occurrence | ||
Homology family | Isomaltase | |
Parent taxon | Newcomers |
Sucrase-isomaltase ( gene : SI ) is the enzyme that the hydrolytic cleavage of limit dextrins , maltotriose , maltose , isomaltose , sucrose and other sugars, multi- catalyzed . This reaction step is essential for the digestion of carbohydrates . The enzyme is found in all vertebrates and is produced in humans in the small intestine and, to a small extent, in the large intestine on the surface of the microvilli . There it is associated with myosin -1A in the cell membrane . Mutations in the SI gene can cause sucrase-isomaltase deficiency and thus sucrose intolerance.
Catalyzed reaction
As an example of the separation of (1 → 6) -alpha-D-glucosidic bonds:
Isomaltose is split into two glucose molecules.
regulation
Activation of the SI gene is associated with changes in the modifications of histone H3 and binding of the transcription factor Cdx-2 to the promoter region of the gene. These requirements are among other things the result of a diet with a high carbohydrate / fat ratio.
HNF-1alpha is involved in the inhibition of gene expression by glucose .
Individual evidence
- ↑ PROSITE: Glycosidase Family 31
- ↑ UniProt P14410
- ↑ Tyska MJ, Mooseker MS: A role for myosin-1A in the localization of a brush border disaccharidase . In: J. Cell Biol. . 165, No. 3, May 2004, pp. 395-405. doi : 10.1083 / jcb.200310031 . PMID 15138292 . PMC 2172191 (free full text).
- ↑ Suzuki T, Mochizuki K, Goda T: Histone H3 modifications and Cdx-2 binding to the sucrase-isomaltase (SI) gene is involved in induction of the gene in the transition from the crypt to villus in the small intestine of rats . In: Biochem. Biophys. Res. Commun. . 369, No. 2, May 2008, pp. 788-793. doi : 10.1016 / j.bbrc.2008.02.101 . PMID 18313392 .
- ↑ Honma K, Mochizuki K, Goda T: Carbohydrate / fat ratio in the diet alters histone acetylation on the sucrase-isomaltase gene and its expression in mouse small intestine . In: Biochem. Biophys. Res. Commun. . 357, No. 4, June 2007, pp. 1124-1129. doi : 10.1016 / j.bbrc.2007.04.070 . PMID 17466947 .
- ↑ Gu N, Adachi T, Matsunaga T, et al : HNF-1alpha participates in glucose regulation of sucrase-isomaltase gene expression in epithelial intestinal cells . In: Biochem. Biophys. Res. Commun. . 353, No. 3, February 2007, pp. 617-622. doi : 10.1016 / j.bbrc.2006.12.065 . PMID 17194452 .