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)

Brush borders were prepared from pig intestinal mucosa and the membrane proteins solubilized with either Triton X-100 or papain. Proteins, thus released, were used as antigens to raise antisera in rabbits. The immunoglobulin G fractions were isolated and shown by the double layer immunofluorescence staining technique to react only with the brush border region of the enterocyte. The antibodies obtained were used in immunoelectrophoretic studies on the brush border proteins. Eight hydrolytic activities were identified by the use of histo-chemical staining methods. These were the microsomal aminopeptidase (EC 3.4.11.2), aspartate aminopeptidase (EC 3.4.11.7), dipeptidyl peptidase IV (EC 3.4.14.X), lactase (EC 3.2.1.23), glucoamylase (EC 3.2.1.3), sucrase (EC 3.2.1.48), isomaltase (EC 3.2.1.10) and alkaline phosphatase (EC 3.1.3.1). In addition, at least four faint immunoprecipitates were formed but none of these were identified.
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PMID:Immunoelectrophoretic studies on pig intestinal brush border proteins. 2 Sep 74

Lactase and maltase, the predominant sugar hydrolases associated with the intestinal brush bordermembrane of the suckling rat, were purified essentially free of the other to near homogeneity (lactase at specific activity 23, maltase at specific activity 58), and their specific physiocochemical properties determined. Antisera prepared to each showed by immunodiffusion a single common precipitin line with pure enzyme and solubilized proteins of the brush border membrane. Brush border membranes were purified 26--35-fold from infant rat intestine. Membranes prepared from 10-day-old rats contained 32% protein, 43% lipid and 25% carbohydrate with lactase and maltase estimated to comprise in excess of 10% and 2%, respectively, of the membrane protein. Immunotitration curves of lactase and maltase showed equivalent antibody binding by the membrane-bound and free enzyme forms. Furthermore, antibody binding to one enzyme did not affect the immunotitration curve or the extractability (by papain or Triton X-100) of the other membrane-bound enzyme. It was concluded that the lactase and maltase molecules are attached singly on the external membrane surface in a spatially independent manner with their antigenic sites as freely available to antibody binding as exhibited by their papain-solubilized counterparts.
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PMID:Sugar hydrolases of the infant rat intestine and their arrangement of the brush border membrane. 11 Mar 47

The arrangement of the sugar hydrolases, sucrase-isomaltase, maltase, and lactase on the microvillus membrane of rat intestine was investigated by immunological technique. The enzymes were purified essentially free of each other to near homogeneity and antisera of high specificity were obtained against each. Microvillus membranes were prepared routinely in high purity from rat intestine and contained an average 61% protein, 20% lipid, and 19% carbohydrate, with the sugar hydrolases comprising an estimated 20--25% of the membrane protein. The immunoreactivity of membrane-bound sucrase-isomaltase, maltase, and lactase was investigated with antisera demostrating specific reactivity to each, when tested in the presence of other membrane extractives. The membrane-bound enzymes were found in each case to combine with antibody in amounts equivalent to that required to effect precipitation of comparable units of the free enzymes from solution. Preloading membrane vesicles with antibodies to any two of the enzymes did not affect either the immunoreactivity or extractability (by papain or Triton X-100) of the third. The antibody-binding studies indicated an arrangement of these enzymes independent of each other on the membrane surface, in a manner allowing each to maintain a high degree of molecular freedom.
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PMID:Sugar hydrolases and their arrangement on the rat intestinal microvillus membrane. 11 6

A brush-border-specific antiserum was raised in rabbits, with Triton X-100-solubilized brush border proteins from pig intestine being used as antigens. The antiserum was used in immunoelectrophoretic studies of brush border proteins solubilized with Triton X-100. Five immunoprecipitates were obtained which corresponded to microsomal aminopeptidase (EC 3.4.11.2), asparate aminopeptidase (EC 3.4.11.7), lactase (beta-galactosidase, EC 3.2.1.23), maltase (exo-1,4-alpha-glucosidase, EC 3.2.1.3) and sucrase-isomaltase (sucrose alpha-glucohydrolase, EC 3.2.1.48). A faint immunoprecipitate was also found for the glycylprolyl dipeptidyl peptidase (EC 3.4.14.-). The brush border proteins were solubilized on a large scale from a brush border membrane preparation by the use of Triton X-100; the peptidases obtained were homogeneous in size and had hydrophobic properties. By chromatography on columns of concanavalin A-Sepharose, hydroxyapatite, Ultrogel AcA 34, DEAE-cellulose and immunosorbent, gamma-glutamyl transpeptidase (gamma-glutamyl transferase, EC 2.3.2.2) and microsomal aminopeptidase were each isolated in separate fractions. Glycylprolyl dipeptidyl peptidase and asparate aminopeptidase were obtained in another fraction. Immunoelectrophoretic, inhibitor and chromatographic studies showed that the intestinal brush border peptidases are similar to the corresponding particulate peptidases obtained from other organs.
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PMID:Intestinal brush border peptidases. 24 83

The human small intestinal brush border proteins were studied qualitatively by crossed immunoelectrophoresis. Brush border membranes were purified from human jejunum and the proteins released by Triton X-100. Rabbits were immunized with the released proteins and by using a double layer immunofluorescence technique the obtained antisera were shown to be specific against the brush border proteins. The precipitates obtained in crossed immunoelectrophoresis were identified by enzymatic staining techniques. Sucrase (EC 3.2.1.48), isomaltase EC 3.2.1.10), maltase (EC 3.2.1.20), phloretin-glucosidase (EC 3.2.1.62), lactase (EC3.2.1.23), microvillus aminopeptidase (aminopeptidase (microsomal), EC 3.4.11.2), dipeptidyl peptidase IV (EC 3.4.14.X), and alkaline phosphatase (EC 3.1.3.1) were identified while asparate aminopeptidase (EC 3.4.11.7), gamma-glutamyl transferase (EC 2.3.2.2) and trehalase (EC 3.2.1.28) could not be visualized. This work demonstrates that cross immunoelectrophoresis can be used in the study of human small intestinal brush border proteins.
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PMID:Immunoelectrophoretic studies on human small intestinal brush border proteins. A qualitative study of the protein composition. 36 59

About 90% of the protein of hamster intestinal brush borders was solubilised in 0.25% (w/v) sodium dodecyl sulphate without total loss of biological activity. Detergent-polyacrylamide gel electrophoresis of the solubilised proteins separated 10-15 bands and partially resolved maltase, lactase, sucrase-maltase, trehalase and alkaline phosphatase activities. The disaccharidases, which were associated with the higher molecular weight proteins, were preferentially solubilised with 0.1%. (w/v) Triton X-100, butanol or papain, whereas Tris and NaI extracted only the lower molecular weight proteins, possible derived from the core filaments. Electrophoresis of brush border proteins metabolically labelled with [14-C] glucosamine suggested that many of the membrane-bound enzymes are glycoproteins. However, chromatography of a papain digest on Sephadex G-200 showed that the sucrase-maltase complex can be separated nearly free of carbohydrate without total loss of activity. The importance of characterizing membrane proteins solubilised by a number of techniques is discussed.
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PMID:Solubilization of brush borders of hamster small intestine and fractionation of some of the components. 113 70

Rat intestinal microvillus membrane contains at least 24 polypeptides, of which 18 can be solubilized using Triton X-114 at 4 degrees C. Upon phase separation at 32 degrees C, 11 proteins separated nearly completely into the detergent-rich phase, while 9 proteins were found exclusively in the aqueous phase. Enzymes which were uniquely included in the detergent phase were alkaline phosphatase, leucine aminopeptidase, gamma-glutamyl transpeptidase, and Ca2+-Mg2+ ATPase. The proteins which were excluded from the detergent phase and found exclusively in the aqueous phase included the disaccharidases (glucoamylase, sucrase-isomaltase, trehalase, lactase) and the ileal receptor for the intrinsic factor-cobalamin complex. Integral membrane proteins can thus be separated during solubilization into two groups prior to further purification or characterization.
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PMID:Phase separation of rat intestinal brush border membrane proteins using Triton X-114. 301 Jul 62

Comparisons between papain- and Triton X-100-solubilized lactase (EC 3.2.1.23) were made in terms of elution from various chromatographic columns and by molecular weight determinations. Using these techniques, no major differences could be detected. Since papain-solubilized enzyme would be cleaved at the hydrophilic-hydrophobic interface and detergent would release the amphipathic enzyme, the lack of detectable differences between purified lactase solubilized by the two agents suggests the existence of a relatively small anchoring moiety in rats when compared to that suggested in previous studies for adult humans.
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PMID:Comparison of detergent versus protease solubilized rat intestinal lactase. 643 55

A number of transmembrane digestive enzymes of the porcine small intestinal brush border membrane were found to be partially Triton X-100-insoluble at 0 degree C and colocalized in gradient centrifugation experiments with the GPI-anchored alkaline phosphatase in low-density, detergent-insoluble complexes commonly known as glycolipid "rafts". Thus, aminopeptidase N (EC 3.4.11.2), aminopeptidase A (EC 3.4.11.7), dipeptidyl peptidase IV (EC 3.4.14.5), and sucrase-isomaltase (EC 3.2.1.48-10) were 34-48% detergent-insoluble. Maltase-glucoamylase (EC 3.2.1.20) was markedly less detergent-insoluble (20%), and lactase-phlorizin hydrolase (EC 3.2.1.23-62) was essentially fully soluble in detergent. In radioactively labeled, mucosal explants, the newly synthesized brush border enzymes began to associate with detergent-insoluble complexes while still in their transient, high mannose-glycosylated form, and their insolubility increased to that of the steady-state level soon after they achieved their mature, complex glycosylation, i.e., after passage through the Golgi complex. Detergent-insoluble complexes isolated by density gradient centrifugation were highly enriched in brush border enzymes, and the enrichment was apparent after only 1 h of labeling, where aminopeptidase N, sucrase-isomaltase, and alkaline phosphatase together comprised 25-30% of the total labeled, detergent-insoluble proteins, showing that sorting of newly made brush border membrane proteins into the glycolipid "rafts" does take place intracellularly. I therefore propose that, in the enterocyte, the brush border enzymes are targeted directly from the trans-Golgi network toward the apical cell surface.
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PMID:Involvement of detergent-insoluble complexes in the intracellular transport of intestinal brush border enzymes. 784 19

Leishmania donovani promastigotes were collected, washed, resuspended in buffer, and assayed for sucrase activity. No activity was observed in the intact washed cells, but activity was measurable when the cells were permeabilized with Triton X-100. Intracellular sucrase activity was highest in promastigotes grown at pH 7.4, somewhat lower in promastigotes grown at pH 5.5, and significantly lower in "amastigotes" grown at pH 5.5. No trehalase, lactase, or maltase activities were observed. Assay of the medium in which the cells had grown showed that most the sucrase activity was extracellular, i.e. was secreted into the medium during growth.
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PMID:Secretion of sucrase by Leishmania donovani. 804 86


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