Abstract |
Enzymatic activity, biosynthesis, and maturation of lactasephlorizin hydrolase (LPH) were investigated in adult volunteers with suspected lactose intolerance. Mean LPH activity in jejunal biopsy homogenates of these individuals was 31% compared to LPH-persistent individuals, and was accompanied by a reduced level of LPH- protein. Mean sucrase activity in individuals with low LPH was increased to 162% and was accompanied by an increase in sucrase- isomaltase (SI)- protein. Biosynthesis of LPH, SI, and aminopeptidase N (APN) was studied in organ culture of small intestinal biopsy specimens. In individuals with LPH restriction, the rate of synthesis of LPH was drastically decreased, reaching just 6% of the LPH-persistent group after 20 h of culture, while the rate of synthesis of SI appeared to be increased. In addition, maturation of pro-LPH to mature LPH occurred at a slower rate in LPH-restricted tissue. Immunoelectron microscopy revealed an accumulation of immunoreactive LPH in the Golgi region of enterocytes from LPH-restricted individuals and reduced labeling of microvillus membranes. Therefore, lactose intolerance in adults is mainly due to a decreased biosynthesis of LPH, either at the transcriptional or translational level. In addition, intracellular transport and maturation is retarded in some of the LPH-restricted individuals, and this leads to an accumulation of newly synthesized LPH in the Golgi and a failure of LPH to reach the microvillus membrane.
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Authors | E E Sterchi, P R Mills, J A Fransen, H P Hauri, M J Lentze, H Y Naim, L Ginsel, J Bond |
Journal | The Journal of clinical investigation
(J Clin Invest)
Vol. 86
Issue 4
Pg. 1329-37
(Oct 1990)
ISSN: 0021-9738 [Print] United States |
PMID | 1976654
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Methionine
- Sucrase-Isomaltase Complex
- beta-Galactosidase
- Lactase-Phlorizin Hydrolase
- Aminopeptidases
- CD13 Antigens
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Topics |
- Adult
- Aminopeptidases
(biosynthesis)
- CD13 Antigens
- Humans
- Intestines
(enzymology)
- Lactase-Phlorizin Hydrolase
(analysis, biosynthesis, immunology)
- Lactose Intolerance
(enzymology)
- Methionine
(metabolism)
- Microvilli
(enzymology)
- Sucrase-Isomaltase Complex
(biosynthesis)
- beta-Galactosidase
(analysis, biosynthesis, immunology)
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