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Molecular aspects of disaccharidase deficiencies.
- Source :
-
Bailliere's clinical gastroenterology [Baillieres Clin Gastroenterol] 1990 Mar; Vol. 4 (1), pp. 79-96. - Publication Year :
- 1990
-
Abstract
- We have described the methods used for studying the biosynthesis and the post-translational processing of sucrase-isomaltase (SI), lactase-phlorizin hydrolase (LPH) and maltase-glucoamylase (MGA) in human small intestinal mucosa. Our results are discussed in the context of findings by other researchers. A surprising finding coming out of all these studies is that SI, LPH and MGA are structurally quite different. SI and LPH are both synthesized as large molecular weight precursors which are proteolytically processed to the mature enzymes. In the case of SI, this processing occurs after insertion of the precursor into the brush border membrane and is catalysed by pancreatic proteases; the mature form consists of the two subunits sucrase and isomaltase, the latter containing an N-terminal peptide anchor. Proteolytic processing of the LPH-precursor occurs intracellularly, yielding a mature enzyme in the form of a two active site polypeptide which is anchored via a C-terminal peptide. The role of the large cleaved propolypeptide of LPH is not yet known. MGA is the largest of the three disaccharidases, having a molecular weight of greater than 300 kDa. No proteolytic processing seems to be taking place during biogenesis of MGA in human mucosa, and the mode of attachment to the membrane is unknown at present. The application of the methods described to the investigation of congenital sucrase-isomaltase deficiency (CSID) and lactase restriction in adults is presented and differences between CSID and LPH restriction are discussed.
- Subjects :
- Disaccharidases chemistry
Disaccharidases genetics
Glucan 1,4-alpha-Glucosidase deficiency
Humans
Immunologic Techniques
Intestines enzymology
Lactase
Lactase-Phlorizin Hydrolase deficiency
Microvilli enzymology
Organ Culture Techniques
Sucrase-Isomaltase Complex chemistry
Sucrase-Isomaltase Complex deficiency
Sucrase-Isomaltase Complex genetics
alpha-Glucosidases deficiency
beta-Galactosidase deficiency
Disaccharidases deficiency
Subjects
Details
- Language :
- English
- ISSN :
- 0950-3528
- Volume :
- 4
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Bailliere's clinical gastroenterology
- Publication Type :
- Academic Journal
- Accession number :
- 2119833
- Full Text :
- https://doi.org/10.1016/0950-3528(90)90040-n