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)

Age-specific changes in glycosylation of rat intestinal lactase-phlorizin hydrolase were analyzed using enzyme immunoprecipitated from microvillus membranes of suckling, weaning, and adult rats, and carbohydrate moieties were examined by lectin affinity binding, metabolic labeling, and neuraminidase treatment. Lectin binding indicated the presence of N-linked and O-linked oligosaccharide chains containing mannose and galactose throughout development. An age-dependent shift in sialic acid and fucose was seen during the period of weaning; no fucose was detectable in lactase-phlorizin hydrolase until after the rats were 20 days of age, whereas sialic acid was reduced in adult lactase-phlorizin hydrolase. The presence of sialic acid in suckling intestines and fucose in adult was confirmed by metabolic labeling with appropriate radioactive precursors. Sodium dodecyl phosphate-polyacrylamide gel electrophoresis analysis of immunoprecipitated lactase-phlorizin hydrolase from the proximal and mid small intestine showed two bands of approximately 220 and 130 kilodaltons in all age groups. In the distal part of the adult small intestine, lactase-phlorizin hydrolase appeared as two bands of similar size to those found in the proximal and mid portions. In contrast, during the suckling and weaning periods, these distal bands were approximately 225 and 135 kilodaltons. [35S]-methionine labeling and fluorography of neonatal intestines confirmed these observations. The size difference between proximal and distal small intestines was virtually eliminated by neuraminidase treatment. These data indicate that the core structure of microvillus membrane lactase-phlorizin hydrolase, consisting of both N-linked and O-linked oligosaccharides, remains constant during development, although terminal sugars shift from predominantly sialic acid during the suckling period to fucose in adulthood. This alteration in glycosylation of the protein occurs in a different pattern from the postweaning decline in lactase specific activity. Consequently, age-dependent changes in glycosylation cannot account for the decrease in lactase-phlorizin hydrolase-specific activity observed during development.
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PMID:Glycosylation of lactase-phlorizin hydrolase in rat small intestine during development. 210 55

When studying mucosal barrier function of developing animals, we noted that intestinal microvillus membranes (MVM) of newborn animals differ in their fluidity and binding characteristics to lectins compared with adult MVM. To further investigate these differences and determine whether maturation of the microvillus surface could be accelerated in utero, pregnant rats were given intraperitoneal cortisone beginning on the 17th day of gestation. Control and cortisone-treated animals were allowed to deliver normally, and the small intestines from newborns were used to isolate MVM. Microvillus membrane surface characteristics were evaluated by employing an 125I-labeled fucose-specific lectin, Ulex europeus (UEA). Changes in MVM proteins were monitored by disaccharidase activities and sodium dodecyl sulfate-polyacrylamide electrophoresis. MVM fluidity was accessed using a 5-doxyl stearic acid label and electron-spin-resonance spectroscopy. Results from these studies indicate that the birth weights of newborn rats exposed to cortisone in utero were significantly reduced; sucrase activity was prematurely induced and specific activities of lactase and maltase were enhanced in the intestines of the cortisone-treated newborns as contrasted with control animals. Furthermore, binding of 125I-UEA to MVM was greatly increased in treated animals. MVM fluidity decreased (P less than 0.001) compared with control animals and resembled the structural characteristics of more mature MVM. These results suggest that cortisone exposure in utero accelerate maturation of the microvillus surface of enterocytes.
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PMID:Development of gastrointestinal mucosal barrier. VII. In utero maturation of microvillus surface by cortisone. 299 Feb 36

The adult guinea-pig small intestinal microvillus membrane was purified approximately 25-fold by both cation-precipitation and differential centrifugation methods. Comparison by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed no substantial differences in polypeptide composition between the two preparations. One-dimensional SDS-PAGE and two-dimensional isoelectric focussing (IEF)/SDS-PAGE, together with Coomassie-blue, silver and lectin-staining, showed three major high molecular weight polypeptides, Mr 108 000, 116 000 and 127 000, as well as a 47 kDa protein (actin), as major constituents of the membrane. The proteins of Mr 108 000 and 116 000 were strongly concanavalin A reactive. A detailed two-dimensional IEF/SDS-PAGE map of the membrane was constructed. Sodium carbonate treatment showed the two concanavalin A-reactive glycoproteins, Mr 108 000 and 116 000, comprising the sucrase-isomaltase complex, to be loosely-associated 'extrinsic' microvillus membrane proteins. Two proteins, Mr 127 000 and 135 000, were tightly-associated 'intrinsic' microvillus proteins. Despite regional differences in specific activity of some small intestinal microvillar enzymes, most noticeably enterokinase (EC 3.4.21.9) and dipeptidyl peptidase IV (EC 3.4.14.x), no substantial regional differences were seen in microvillus membrane polypeptide composition. In contrast, a substantial increase in the major high molecular weight proteins of Mr 108 000 and 116 000 accompanied a 10-fold rise in sucrase-isomaltase activity, and loss of a major protein of Mr 131 000 accompanied the complete loss of lactase activity from the membrane during postnatal development.
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PMID:Two-dimensional isoelectric focussing/sodium dodecyl sulphate polyacrylamide gel electrophoretic mapping and some molecular characteristics of the proteins of the adult guinea-pig small intestinal microvillus membrane. 399 21

The central aspect of epithelial cells is their polarized structure, characterized by two distinct domains of the plasma membrane, the apical and the basolateral membrane. Apical protein sorting requires various signals and different intracellular routes to the cell surface. The first apical targeting motif identified is the membrane anchoring of a polypeptide by glycosyl-phosphatidyl-inositol (GPI). A second group of apical signals involves N- and O-glycans, which are exposed to the luminal side of the sorting organelle. Sucrase-isomaltase (SI) and lactase-phlorizin hydrolase (LPH), which use separate transport platforms for trafficking, are two model proteins for the study of apical protein sorting. In contrast to LPH, SI associates with sphingolipid/cholesterol-enriched membrane microdomains or "lipid rafts". After exit form the trans-Golgi network (TGN), the two proteins travel in distinct vesicle populations, SAVs (SI-associated vesicles) and LAVs (LPH-associated vesicles) . Here, we report the identification of the lectin galectin-3 delivering non-raft-dependent glycoproteins in the lumen of LAVs in a carbohydrate-dependent manner. Depletion of galectin-3 from MDCK cells results in missorting of non-raft-dependent apical membrane proteins to the basolateral cell pole. This suggests a direct role of galectin-3 in apical sorting as a sorting receptor.
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PMID:Requirement for galectin-3 in apical protein sorting. 1648 76

The main objective of this study was to determine the effect of fiber source and concentration on morphological characteristics, mucin staining pattern, and mucosal enzyme activities in the gastrointestinal tract of pigs. The experiment included 50 pigs from 10 litters weaned at 4 wk of age (BW 8.6 +/- 1.4 kg) and divided into 5 treatment groups. Diets containing fiber of various physico-chemical properties and concentrations were formulated to contain 73, 104, or 145 g of dietary fiber/kg of DM. The diets were based on raw wheat and barley flours. Pectin and barley hulls, representing soluble and insoluble fiber sources, respectively, were used to increase the fiber concentration. The pigs were fed the experimental diets for 9 d, and then the pigs were euthanized and the entire gastrointestinal tract was removed. Tissue samples were taken from the mid and distal small intestine and from the mid colon. Inclusion of pectin in the diets significantly decreased (P < 0.001) ADFI and ADG compared with pigs fed no pectin. The villi and the crypts were shorter in pigs fed pectin-containing diets, but the villous height/crypt depth ratio was unaltered. Pectin significantly decreased the area of mucins in the crypts of the small intestine, indicating that the pigs fed the pectin-containing diet would probably be more susceptible to pathogenic bacteria, although this cannot be separated from the impact on ADFI. The lectin-binding pattern of the intestinal mucosa was unaffected by diet. The activity of lactase and maltase was increased in pigs fed diets with high fiber content, whereas sucrase activity was increased in pigs fed the pectin-containing diets. The activity of the peptidases, aminopeptidase N and dipeptidylpeptidase IV, was increased when feeding high fiber diets, whereas the activity of gamma-glutamyl transpeptidase remained unaffected by the experimental diets. In conclusion, the reduced feed intake observed with the pectin-containing diets could explain the lower villous height and crypt depth observed in this study. However, direct effects of pectin also are possible, and thus further study is warranted. Feeding pigs high insoluble fiber diets improved gut morphology by increasing villi length and increased mucosal enzyme activity when compared with pigs fed pectin-containing diets. The mucin content as determined by staining characteristics suggests that pigs fed high insoluble fiber diets might be better protected against pathogenic bacteria than pigs fed diets high in soluble fiber.
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PMID:Intestinal morphology and enzymatic activity in newly weaned pigs fed contrasting fiber concentrations and fiber properties. 1669 94

Human colon adenocarcinoma cells (HT29-ATCC) and the clone HT29-5F7 were cultured under conditions that differentiate cells to a polarized intestinal phenotype. Differentiated cells showed the presence of junctional complexes and intercellular lumina bordered by microvilli. Intestinal brush border hydrolase activities (sucrase, aminopeptidase N, lactase and maltase) were detected mainly in differentiated HT29-ATCC cells compared with the differentiated clone, HT29-5F7. The presence of non-GM1 receptors of Escherichia coli heat-labile enterotoxin (LT-I) on both types of differentiated HT29 cells was indicated by the inability of cholera toxin B subunit to block LT-I binding to the cells. Binding of LT-I to cells, when GM1 was blocked by the cholera toxin B subunit, was characterized by an increased number of LT-I receptors with respect to undifferentiated control cells. Moreover, both types of differentiated cells accumulated higher amounts of cyclic AMP in response to LT-I than undifferentiated cells. Helix pomatia lectin inhibited the binding of LT-I to cells and the subsequent production of cyclic AMP. LT-I recognized blood group A-active glycosphingolipids as functional receptors in both HT29 cell lines and the active pro-sucrase form of the glycoprotein carrying A-blood group activity present in HT29-ATCC cells. These results strongly suggest that LT-I can elicit an enhanced functional response using blood group A-active glycoconjugates as additional receptors on polarized intestinal epithelial cells.
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PMID:Functional interaction of Escherichia coli heat-labile enterotoxin with blood group A-active glycoconjugates from differentiated HT29 cells. 1688 90

The aim of this study was to obtain information that could help to ease the weaning transition in commercial pig production. Before weaning, phytohemagglutinin (PHA) in the form of a crude preparation of red kidney bean lectin was fed by gavage to 24 crossbred [(Swedish Landrace x Yorkshire) x Hampshire] piglets, whereas 24 control piglets were fed alpha-lactalbumin by gavage, to study the effect on growth, occurrence of postweaning diarrhea, feeding behavior, and some anatomical and physiological traits of the gastrointestinal tract. Within the litter, piglets were randomly assigned to PHA treatment or control and remained in the same pen from the beginning (PHA exposure at 7 d before weaning) until the end of the experiment (14 d post-weaning). Weaning took place at the age of 31 to 34 d. Pigs treated with PHA grew faster (P = 0.013) during the first week postweaning and tended to have lower total diarrhea scores (P = 0.10) than did control pigs. On d 5 after weaning, piglets treated with PHA spent more time eating (P = 0.028) than control pigs. No immunostimulating effect of PHA, measured by plasma immunoglobulin G, could be detected. An increase in the intestinal barrier properties before weaning, as a response to PHA treatment, was demonstrated in intestinal absorption studies using Na-fluorescein and BSA as gavage-fed markers. Less uptake (measured as plasma concentrations) of the marker molecule Na-fluorescein occurred during a 24-h study period, and numerically lower levels of BSA were observed compared with studies in control pigs of the same age. A total of 12 pigs (6 control, 6 PHA-treated) were euthanized on the day of weaning for analyses of gastrointestinal properties. The PHA-treated pigs tended to have a longer total small intestinal length (P = 0.063) than that of the control pigs. The enzyme profile of the jejunal epithelium responded to PHA exposure with a decrease in lactase activity and an increase in maltase and sucrase activities, which is similar to changes normally observed after weaning. No differences were found in the size of the pancreas or in its contents of trypsin and amylase. In conclusion, exposing piglets to crude, red kidney bean lectin for 3 d during the week before weaning led to changes in performance and small intestinal functional properties that would be expected to contribute to a more successful weaning.
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PMID:Effects of crude red kidney bean lectin (phytohemagglutinin) exposure on performance, health, feeding behavior, and gut maturation of pigs at weaning. 1704 Sep 48

The dietary lectin phytohaemagglutinin (PHA) induces gut growth and precocious maturation in suckling rats after mucosal binding. The present study investigated the dose range in which PHA provokes gut maturation and if it coincided with immune activation. Suckling rats, aged 14 d, were orogastrically fed a single increasing dose of PHA: 0 (control), 2, 10, 50 or 250 microg/g body weight (BW) in saline. The effect on gut, lymphoid organs and appearance of CD3+ (T-lymphocyte) and CD19+ (B-lymphocyte) cells in the small-intestinal mucosa was studied at 12 h (acute) and 3 d (late phase) after treatment. The low PHA doses (2 and 10 microg/g BW) induced intestinal hyperplasia without mucosal disarrangement but did not provoke gut maturation. Only the high PHA doses (50 and 250 microg/g BW) temporarily disturbed the intestinal mucosa with villi shortening and decrease in disaccharidase activities, and later after 3 d provoked precocious maturation, resulting in an increase in maltase and sucrase activities and decrease in lactase activity and disappearance of the fetal vacuolated enterocytes in the distal small intestine. Exposure to the high, but not to the low, PHA doses increased the number of mucosal CD19+ and CD3+ cells in the small intestine after 12 h, a finding also observed in untreated weaned rats aged 21-28 d. In conclusion, there was a dose-related effect of PHA on gastrointestinal growth and precocious maturation that coincided with a rapid expansion of mucosal B- and T-lymphocytes, indicating a possible involvement of the immune system in this process.
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PMID:Precocious gut maturation and immune cell expansion by single dose feeding the lectin phytohaemagglutinin to suckling rats. 1864 65

Lactase exists in both soluble and membrane-bound forms in suckling rat intestine. The distribution of lactase and its glycosylated isoforms in response to thyroxine or cortisone administration has been studied in suckling rats. 75% of lactase activity was detected, associated with brush borders, compared to 24% in the soluble fraction of 8-day-old rats. Thyroxine treatment enhanced soluble lactase activity to 34%, whereas particulate fraction was reduced to 67% compared to controls. Cortisone administration reduced soluble lactase activity from 24% in controls to 12% with a concomitant increase in membrane-bound activity to 89%. Western blot analysis revealed lactase signal, corresponding to 220 kDa in both the soluble and membrane fractions, which corroborated the enzyme activity data. The elution pattern of papain solubilized lactase from agarose-Wheat Germ agglutinin, or Concanavalin A or Jacalin agglutinin columns was different in the suckling and adult rat intestines. Also the elution profile of lactase activity from agarose-lectin columns was modulated in cortisone, thyroxine, and insulin injected pups, which suggests differences in glycosylated isoforms of lactase under these conditions. These findings suggest the role of these hormones in inducing changes in lactase glycosylation during postnatal development of intestine, which may contribute to adult-type hypolactasia in rats.
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PMID:Hormone induced changes in lactase glycosylation in developing rat intestine. 1871 86