Sucrase isomaltase

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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+ H 2 O ⇒ 2D-glucose

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

  1. ↑ PROSITE: Glycosidase Family 31
  2. ↑ UniProt P14410
  3. ↑ 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).
  4. ↑ 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 .
  5. ↑ 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 .
  6. ↑ 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 .

Web links

Wikibooks: Biochemistry and Pathobiochemistry: Glycogenolysis and Starch Breakdown  - Learning and Teaching Materials