Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.20 (alpha-glucosidase)
4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Highly purified microvillus membrane vesicles isolated from rat small intestine were enriched in sucrase, maltase, and aminopeptidase activities. Approximately 90-95% of each enzyme was released from the membrane fraction by treatment with detergent (Triton X-100) and sonication. Using untreated and solubilized preparations, the effect of lectin binding on the activity of each of the three enzymes was measured. It was observed that wheat germ agglutinin (WGA) and phytohemagglutinin (PHA) dramatically enhanced the activity of membrane-bound maltase but had much less effect on the detergent solubilized enzyme. Under the same conditions aminopeptidase activity was inhibited by WGA and PHA while sucrase activity was not affected. These alterations in enzyme activity occurred at lectin concentrations that also precipitated each solubilized enzyme from solution. Inhibitory sugars prevented the alterations in enzyme activity suggesting that the effect is due to the binding of lectin to specific carbohydrate structures. Enhancement of membrane-bound maltase activity by WGA and PHA was shown to be temperature dependent indicating that the lipid environment of the microvillus membrane may play a role in mediating the lectin effect. A kinetic analysis of the changes in maltase activity induced by these two lectins was due solely to an increase in Vmax. Two other lectins used in this study (concanavalin A and Ricinus communis agglutinin) did not readily precipitate the enzymes in question or alter their activity. These results show that binding of lectins to brush border membranes can induce variable changes in the activity of several membrane associated hydrolases, and suggest that similar changes may occur in vivo in the presence of dietary lectin.
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PMID:Effect of lectins on the activity of brush border membrane-bound enzymes of rat small intestine. 390 78

1. Brush borders were isolated from rabbit kidney-cortex homogenates by rate-zonal centrifugation through a sucrose density gradient in a B-XIV zonal rotor, followed by differential centrifugation. 2. The method of preparation gave brush borders of high purity with a reasonable yield. The morphological appearance supported the evidence from enzymic and chemical investigations, that the brush borders were only slightly contaminated with endoplasmic reticulum, mitochondria, lysosomes and nuclei. 3. The molar ratio of cholesterol to phospholipid lay within the range found in other plasma membranes, but the carbohydrate content was double that found in liver plasma membranes. 4. Alkaline phosphatase, maltase, trehalase and aminopeptidase were major enzymic constituents of the brush borders, and had an approximately equal yield and enrichment, but none of these enzymes fulfilled the criteria for marker enzymes. 5. Mg(2+)-dependent and Na(+),K(+)-dependent adenosine triphosphatases, although found in brush borders, had low yields and low enrichments.
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PMID:Isolation and characterization of rabbit kidney brush borders. 426 1

The longitudinal distribution of different brush border enzymes along the human small intestine was studied by crossed immunoelectrophoresis. The results are based on biopsies taken every 50 cm in three intestines obtained at autopsy and on peroral or peroperative biopsies from the ligament of Treitz, proximal jejunum and distal ileum from 11 patients undergoing jejunoileal bypass operation for obesity. Lactase-phlorizin hydrolase (EC 3.2.1.23-62) and sucrase-isomaltase(EC 3.2.1.48-10) had their highest level in jejunum with decreasing activity towards the proximal and distal ends of the intestine, while maltase (EC 3.2.1.20) increased along the intestine and reached its highest activity in the distal ileum. A carboxypeptidase (EC 3.4.12.X) is demonstrated as an enzymatic entity of the human intestine. This enzyme had a rather flat distribution curve while microvillus aminopeptidase (EC 3.4.11.2), dipeptidyl peptidase IV (EC 3.4.14.X) and aspartate aminopeptidase (EC 3.4.11.7) all increased along the length axis and reached maximum values in distal ileum.
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PMID:Immunoelectrophoretic studies on human small intestinal brush border proteins--the longitudinal distribution of peptidases and disaccharidases. 611 68

The amounts of lactase (beta-D-galactosidase, EC 3.2.1.23), sucrase (sucrose alpha-D-glucohydrolase, EC 3.2.1.48), maltase (alpha-D-glucosidase, EC 3.2.1.20) microvillus aminopeptidase (EC 3.4.11.2) and dipeptidyl peptidase IV (EC 3.4.14.-) in tangentially sectioned biopsies from jejunum were studied by quantitative immunoelectrophoresis and enzymic assays. All enzymes had their maximum activities near the mid-region of the villi and their lowest activities at the bases of the crypts. The ratio between enzyme activity and immunoreactive protein was constant along the villus-crypt axis. This result is consistent with a continuous brush-border-enzyme synthesis as the enterocytes migrate up the villi.
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PMID:Immunoelectrophoretic studies on human small-intestinal brush-border proteins. 611 34

The long-term (28 days) effects of feeding two glucocorticoids, prednisolone and betamethasone 17-valerate, on the adult rat jejunum were examined. Both steroids increased the activities of microvillus enzymes, alpha-glucosidase, aminopeptidase, and gamma-glutamyltransferase, measured in isolated epithelial cells by 46-83%. However, betamethasone 17-valerate caused striking epithelial hypoplasia such that microvillus enzyme activity per centimeter of intestine was similar to that of control rats. Prednisolone produced a trivial epithelial hypoplasia, and therefore microvillus enzyme activity per centimeter of intestine was increased. D-Galactose absorption measured in vivo was similarly affected by the two steroids. D-Galactose absorption per centimeter of intestine was increased after prednisolone but unchanged after betamethasone 17-valerate. Thus, glucocorticoids have separate and opposing actions on the function and structure of the adult rat small intestine: a) to increase the digestive-absorptive function of the mature epithelial cell and b) to decrease the epithelial cell population. These findings suggest that the effect of any particular glucocorticoid on intestinal function will depend on the extent to which these opposing actions predominate.
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PMID:Differential effect of glucocorticoids on structure and function of adult rat jejunum. 611 32

An epithelial intestinal cell line has been established from explants of fetal rat small intestine. After the 9th passage (approx. 25 population doublings) epithelial-like cells acquired the properties of a permanent cell line. The epithelial nature of this cell line, and of clone IRD 98 subsequently isolated, is supported by morphological and ultrastructural criteria, and also by the presence of enzymes characteristic of enterocytes, such as aminopeptidase, alkaline phosphatase, gamma-glutamyl transferase, lactase and maltase. The occurrence of the triglyceride pathway enzyme monoacylglycerol acyltransferase and of apoproteins (Apo A1 and Apo E) can also be demonstrated. Taken together, the results presented here provide evidence that clone IRD 98 is an epithelial cell line, most likely originating from the relatively differentiated cell layer of fetal rat small intestine.
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PMID:Establishment and characterization of an epithelial intestinal cell line from rat fetus. 613 30

Five Beagle dogs, equipped with duodenal and gastric fistulae, were fed a standard diet before receiving the same diet supplemented with wheat bran for 1 month. Pancreatic secretory investigations performed in conscious animals before and 1 month after bran administration showed a significant parallel increase in the flow rate of pancreatic secretion and the outputs of bicarbonate and amylase both in basal and secretin-stimulated conditions. The outputs of protein and chymotrypsin increased only in unstimulated secretions, while the output of lipase was strongly reduced in response to secretin. However, the small intestinal mucosa was not affected by bran administration. Dietary fiber did not alter the height of the villi or the activity of sucrase, maltase and aminopeptidase in mucosal homogenates or isolated brush border membranes from intestinal biopsies. These data suggest that wheat bran supplemented to the standard diet affects the exocrine pancreatic secretion but not intestinal enzyme activities involved in the absorption of carbohydrates and proteins in the dog.
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PMID:Effects of wheat bran on the exocrine pancreas and the small intestinal mucosa in the dog. 620 61

Antibodies against 3 purified human small intestinal brush-border hydrolases (sucrase-isomaltase, maltase-glucoamylase and neutral aminopeptidase) were produced in rabbits. By double immunodiffusion and crossed immunoelectrophoresis the antisera appeared to be monospecific. However, with the immunoblotting method antibodies reacting with many brush-border proteins were detected. In one case, the cross-reactions were due to the presence of anti-A antibodies. In other cases absorption of the antisera with absorbants with blood group A and H activities did not eliminate these reactions. As the main brush-border proteins are glycosylated and share common lectin reactivities, it is possible that these antibodies are directed against carbohydrate antigens. The use of such antibodies for immunocytochemical methods and for immunoassays must be undertaken with caution. These principles are applicable to other antigen systems.
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PMID:Antigenic cross-reactions among human intestinal brush-border enzymes revealed by the immunoblotting method and rabbit anti-enzyme sera. 620 83

The hybridoma technique, originally developed by G. Kohler & C. Milstein, is a powerful new experimental approach for analysis of complex biological systems, and is particularly suited for identification and study of surface-membrane antigens. This technique has been used for the production of monoclonal antibodies to intestinal brush border membrane proteins. Spleen cells, obtained from BALB/c mice immunized with purified brush border membranes, were fused with NSI mouse myeloma cells, and hybrids were selected with a culture medium containing hypoxanthine, aminopterin and thymidine (HAT medium). Hybridoma cultures were screened for production of specific antibodies by radio-immunobinding assays and by immunofluorescent staining of intestinal frozen sections. Selected hybridoma cultures were cloned twice and used for the production of large amounts of antibodies, which were characterized. Nineteen monoclonal antibodies have been prepared to date, about half of them specifically staining the brush border membrane of mature enterocytes. Ten of the antibodies specifically immunoprecipitate surface-membrane proteins, which were analysed by sodium dodecyl sulphate slab-gel electrophoresis, by two-dimensional slab-gel electrophoresis, and by specific enzyme assays. Two antibodies were found to be specific for sucrase-isomaltase, one for an aminopeptidase, two for an isoenzyme of alkaline phosphatase that is present exclusively in the proximal small intestine, and one for maltase-glucoamylase. These monoclonal antibodies, and others prepared by similar techniques from mice immunized with a wide variety of intestinal subcellular fractions, should prove invaluable tools for the study of the biosynthesis of cell-surface proteins, the fetal and postnatal development of specific intestinal functions, and the process of cell differentiation in the intestinal epithelium.
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PMID:Use of monoclonal antibodies in the study of intestinal structure and function. 634 93

A 90% jejunoileal bypass induces in the rat a protein malnutrition state which is characterized (1) by the decreased level of plasma proteins and albumins and (2) by the reduced level of most essential and non-essential plasma amino acids. In the exocrine pancreas there was a decreased content of digestive enzymes, especially of amylase, while the secretion of enzymes studied in vitro was reduced. In the ileum left in one piece, the specific activities of maltase and sucrase increased significantly while aminopeptidase was unaffected. It is suggested that exocrine pancreatic insufficiency observed after small bowel bypass in the rat might contribute to protein malnutrition (1) by producing maldigestion and (2) by inducing an imbalance in intestinal enzymes favouring a preferential absorption of carbohydrates compared to proteins, thus emphasizing the protein malnutrition state.
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PMID:Protein malnutrition after jejunoileal bypass in the rat. Possible contribution of the exocrine pancreas and the included intestine. 642 94


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