Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.108 (lactase)
 2,133 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of intestinal bacterial over-growth on brush border hydrolases and brush border glycoproteins was studied in nonoperated control rats, control rats with surgically introduced jejunal self-emptying blind loops, and rats with surgically introduced jejunal self-filling blind loops. Data were analyzed from blind loop segments, segments above and below the blind loops, and three corresponding segments in the nonoperated controls. Rats with self-filling blind loops had significantly greater fat excretion than controls and exhibited significantly lower conjugated:free bile salt ratios in all three segments. Maltase, sucrase, and lactase activities were significantly reduced in homogenates and isolated brush borders from the self-filling blind loop, but alkaline phosphatase was not affected. The relative degradation rate of homogenate and brush border glycoproteins was assessed by a double-isotope technique involving the injection of d-[6-(3)H]glucosamine 3 h and d-[U-(14)C]glucosamine 19 h before sacrifice, and recorded as a (3)H:(14)C ratio. The relative degradation rate in both homogenate and brush border fractions was significantly greater in most segments from rats with self-filling blind loops. In the upper and blind loop segments from rats with self-filling blind loops, the (3)H:(14)C ratios were higher in the brush border membrane than in the corresponding homogenates, indicating that the increased rates of degradation primarily involve membrane glycoproteins. Incorporation of d-[6-(3)H]glucosamine by brush border glycoproteins was not reduced in rats with self-filling blind loops, suggesting that glycoprotein synthesis was not affected. Polyacrylamide gel electrophoresis of brush border glycoproteins from the contaminated segments indicated that the large molecular weight glycoproteins, which include many of the surface hydrolases, were degraded most rapidly. Brush border maltase, isolated by immunoprecipitation, had (3)H:(14)C ratios characteristic of the most rapidly degraded glycoproteins. The results indicate that bacteria enhance the destruction of intestinal surface glycoproteins including disaccharidases. Since alkaline phosphatase, a glycoprotein, is not affected, the destruction is selective and presumably involves only the most exposed membrane components.
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PMID:Pathogenesis of mucosal injury in the blind loop syndrome. Brush border enzyme activity and glycoprotein degradation. 41 Aug 30

1. The proteins of the intestinal microvillus membrane have been studied during post-natal development in the rat (days 12--37). 2. In suckling animals (up to age 20 days), the majority of alkaline phosphatase, glucoamylase and lactase activities in the distal half of the intestine were located in the supernatant fraction (100000 X g, 60 min). These enzymes were attached to the membrane from the proximal intestine at all ages. 3. Alkaline phosphatase, maltase and lactase activities in the supernatant fractions chromatographed in Sephadex G-200 in positions similar to the corresponding membrane enzyme. Corresponding activities for lysosomal counter-parts of maltase and lactase present in the supernatant fraction chromatographed differently. Moreover, pH optimum of the soluble enzymes was 9.2 for phosphatase and 5.5--6.0 for glycoamylase and lactase. The soluble lactase and alkaline phosphatase were inhibited minimally by p-chloromercuribenzoate, and sodium fluoride respectively. L-Phenylalanine (20 mM) did inhibit the soluble phosphatase by 90%. Thus, the soluble enzymes are not mainly of the lysosomal origin, but have characteristics of membrane-bound enzymes. 4. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate revealed 18 protein bands which were present in adult membranes. Two other proteins were unique for membranes of distal intestine in suckling rats. The proteins corresponding to known enzyme activity changed as expected with age (e.g. sucrase, maltase increased, lactase decreased). Most of the other proteins were also altered in amount during development. Thus, the changes in the microvillus membrane during development in the rat are not limited to specific enzymes.
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PMID:Development of intestinal brush border membrane proteins in the rat. 41 9

Turnover in organ culture of human small intestinal membrane glycoproteins was measured by the pulse-chase technique, using 14C-glucosamine, 14C-fucose or 14C-leucine as tracers. Apparently, low degradation rates were found for the major high-molecular-weight proteins which co-migrated on SDS-polyacrylamide gels with maltase-glucoamylase, lactase-phlorizin-hydrolase and sucrase-isomaltase enzymic activities. In contrast, an unidentified glycoprotein appearing on gels next to alkaline phosphatase exhibited a higher degradation rate with an apparent half-life of about 30 h, this being similar to the half-life of total glycoprotein as measured in mucosal homogenates. The results obtained with the pulse-chase technique were confirmed by double isotope experiments using 14C-leucine and 3H-leucine as tracers. These findings indicate that in organ culture there is a low basic turnover of human intestinal membrane glycoproteins which co-migrate on gels with known glycosidase enzymic activities.
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PMID:Turnover studies of human intestinal brush border membrane glycoproteins in organ culture. 45 41

Jejunal mucosal function and structure was examined in 31 patients with ulcerative colitis and 29 patients with Crohn's disease with ileal, ileocolonic or colonic involvement; A significant reduction of the specific activity of disaccharidases (lactase, sucrase and trehalase) in jejunal mucosal homogenate occurred in patients with inflammatory bowel disease. Similarly, alkaline phosphatase was reduced in ulcerative colitis. Several dipeptidases such as glycyl-leucine, leucyl-glycine, glycyl-glycine and valyl-proline hydrolase activities were lower in patients with inflammatory bowel disease than in controls. Histological changes in jejunal mucosal biopsies occurred in 71% of patients with ulcerative colitis and 61% with Crohn's disease. These changes ranged from mild abnormalities of villus architecture to marked reduction of villus height. Most patients with a reduction in mucosal enzymes had concommitant morphological changes in jejunal mucosal biopsy. The results of this study indicate that functional and structural abnormalities of the jejunal mucosa frequently occur in patients with inflammatory bowel disease without radiologic evidence of proximal small bowel involvement.
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PMID:Abnormalities of jejunal mucosal enzymes in ulcerative colitis and Crohn's disease. 47 7

The roles of extracellular and intracellular mechanisms in the degradation of brush border proteins have been investigated by studying the small intestinal mucosa of dogs with naturally occurring exocrine pancreatic insufficiency. Peroral jejunal biopsies were homogenised and the organelles separated by isopycnic centrifugation on continuous sucrose density gradients. The distributions of marker enzymes for the principal subcellular organelles were determined in the gradients and related to the specific activities in the homogenates. There were increased activities of the brush border carbohydrases zinc-resistant alpha-glucosidase, maltase and sucrase in the pancreatic insufficient animals, but no change in lactase activity. The activity of gamma-glutamyl transferase was also higher in the affected group; the activities of two other brush border enzymes, alkaline phosphatase and leucyl-beta-naphthylamidase, however, were unaltered. These findings with an increase in the modal density of the brush border from 1.20 to 1.22 are consistent with an enhanced glycoprotein content of the microvillus membrane. There were also rises in the activities of lysosomal enzymes. N-Acetyl-beta-glucosaminidase activity was increased in the soluble fractions and the percentage latent enzyme activity was reduced, findings indicative of an increased fragility of the lysosomal membrane. There were no marked alterations in the activities or density gradient distributions of marker enzymes for the other organelles, stressing the specificity of the changes in the brush borders and lysosomes. These findings are compatible with the degradation of certain exposed brush border proteins by pancreatic proteases and suggest that when this is defective, intracellular degradative mechanisms may be stimulated.
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PMID:Biochemical changes in the jejunal mucosa of dogs with naturally occurring exocrine pancreatic insufficiency. 48 65

Adult and suckling (13 days old) rat intestinal brush borders have been purified by the procedure of Schmitz et al. (25). Enzymatic proteins have been separated by polyacrylamide gel electrophoresis. In the adult rat, enzyme proteins have been separated by polyacrylamide gel electrophoresis. In the adult rat, enzyme activities in order from the origin were: maltase/glucoamylase/sucrase-isomaltase (protein band 3), lactase (protein band 5), maltase/sucrase-isomaltase (protein band 6) and alkaline phosphatase (protein bands 8 and 9). In the suckling rat, protein band 5 associated with lactase activity was found to be markedly higher compared to the adult rat. Gels were completely devoid of sucrase-isomaltase activity while protein band 3 was strikingly reduced and protein band 6 absent. After hydrocortisone administration to suckling rats, a new band associated with sucrase-isomaltase activity appeared in position 6, whereas protein band 3 markedly increased with the simultaneous appearance of sucrase-isomaltase activity.
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PMID:Separation and characterization of intestinal brush border enzymes in adult rats and in suckling rats under normal conditions and after hydrocortisone injections. 63 79

The effect of exposure of Channa punctatus to a sub-lethal concentration of lead nitrate on the activities of alkaline phosphatase, acid phosphatase amylase, maltase, lactase, trypsin and pepsin has been investigated. A decrease in the activity of alkaline phosphatase has been recorded after 15 days of exposure but there was no significant change after 30 days. Acid phosphatase showed an elevation in activity of both stages. All the three carbohydrases shows elevation after 15 days, followed by an inhibition after 30 days of treatment. The activity of pepsin and trypsin remained above the normal level throughout the tensure of the experiment reveal that the pattern of alteration in enzyme activities is different in liver and digestive system.
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PMID:Alternations in the activity of some digestive enzymes of Channa punctatus, exposed to lead nitrate. 66 84

A micromethod for the isolation of brush border membrane fragments from single peroral duodenal biopsies, and their subsequent analysis by polyacrylamide gel electrophoresis is described. The quantity of biopsy material used varied between 5 and 15 mg wet weight, leaving enough mucosa for histological examination. By cutting the gels longitudinally into two halves it was possible to identify several maltases, sucrase, isomaltase and lactase and to correlate these enzymatic activities with distinct co-migrating protein peaks. For alkaline phosphatase and enterokinase this correlation was not possible. This method is suitable for the study on single biopsies of the molecular alterations occurring in the various congenital enzyme deficiencies of the human small intestine.
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PMID:A micromethod for separation and identification of digestive enzymes in brush border membrane fragments of single human intestinal biopsies. 66 14

Brush-border membranes were isolated from the rat small intestine and then treated with sodium dodecyl sulphate under non-reducing conditions at room temperature. Analysis of the solubilized components by polyacrylamide-gel electrophoresis identified three major glycoproteins that co-migrate with glucoamylase-maltase-sucrase, lactase and isomaltase-maltase-sucrase activities. High activities of alkaline phosphatase and trehalase were detectable, but they could not be attributed to distinct co-migrating protein bands. Analysis of mucosa from the distal small intestine by the same methods showed a pattern of bands different from that obtained with the proximal intestine, which appeared to correlate with the relative deficiency of some of the enzymes in the distal region.
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PMID:The identification of rat intestinal membrane enzymes after electrophoresis on polyacrylamide gels containing sodium dodecyl sulphate. 69 63

1. Rats were fed with the elemental diet Vivonex for 1 or 3 months and their jejunal histology was compared with that of an equal number of rats fed on a normal diet. 2. After 1 month of Vivonex feeding a significant reduction in the ratio of crypt height: villus height (CH:VH) was found in the Vivonex-fed rats (n = 4) compared with the control rats (n = 4) (P less than 0.05). 3. After 3 months the CH:VH ratio was also reduced in the Vivonex-fed rats (n = 18) compared with control rats (n = 18) (P less than 0.002). Villus height was significantly increased (P less than 0.002) and crypt height decreased (P less than 0.05). 4. Jejunal protein content, alkaline phosphatase and disaccharidase activity were also determined in 12 control and 12 Vivonex-fed rats from the 3 months study. 5. Alkaline phosphatase activity was increased from a control value of 201 +/- 8 to 243 +/- 15 munits/cm in the Vivonex-fed rats (n = 12) (P less than 0.05) but no significant changes in lactase, sucrase or maltase activites were found. The observed decrease in the CH:VH ratio suggested an improved survival of the mature enterocyte population during elemental diet feeding.
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PMID:Small-intestinal changes induced by an elemental diet (Vivonex) in normal rats. 72 6


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