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:3.2.1.26 (invertase)
4,927 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

The subcellular localization of the enzyme invertase in Schizosaccharomyces pombe cells, both repressed and derepressed for synthesis of the enzyme, was studied. Most of the invertase was found to be located outside the plasma membrane and only a small percentage was found to be associated to membranes. A substantial portion of the external enzyme remained firmly bound to cell-wall material. All of the invertase recovered in soluble form from cellular extracts reacted with concanavalin A and with the lectin from Bandeiraea simplicifolia seeds, indicating the presence in the enzyme of a carbohydrate moiety which probably contains terminal mannosyl (or structurally related) and galactosyl residues. The possibility of the presence of two different forms of invertase in S. pombe was considered. An intracellular, soluble form of invertase, devoid of carbohydrate, similar to the small invertase of the budding yeast Saccharomyces cerevisiae, was not found in S. pombe. However, the Michaelis constant for sucrose of the enzyme present in repressed cells was smaller than that of the invertase synthesized under derepressing conditions, although this difference could also be the result of a different pattern of glycosylation of the invertase synthesized under different growth conditions.
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PMID:Subcellular localization and glycoprotein nature of the invertase from the fission yeast Schizosaccharomyces pombe. 406 84

The immature sugar cane stalks studied contained less than 7% sucrose, and showed the activities of enzymes such as invertase, alpha-galactosidase, alpha-mannosidase, beta-N-acetylglucosaminidase, beta-glucosidase, beta-xylosidase, and beta-galactosidase. The alpha-galactosidase was highly purified by ammonium sulfate fractionation, gel filtration on a Sephadex G-100 column, ionexchange chromatography on DEAE-cellulose, and CM-cellulose columns, and heat treatment (60 degrees C, 15 min) in the presence of 0.2 m D-galactose. In polyacrylamide gel electrophoresis, the purified enzyme was homogeneous, having a molecular weight of approximately 46,000. In gelfiltration, it was approximately 47,000. The activity was optimum at pH 4.5 and at 60 degrees C. The purified enzyme hydrolyzed p-nitrophenyl-alpha-D-galactopyranoside (Km, 0.83 mM; Vmax, 25.0 mumol/mg/min), raffinose (Km, 25.9 mM; Vmax, 15.4 mumol/mg/min), and stachyose (Km, 13.0 mM; Vmax 2.7 mumol/mg/min), in addition to melibiose, guar gum, and locust bean gum. The hydrolysis of p-nitrophenyl-alpha-D-galactopyranoside was markedly inhibited by HgCl2, AgNO3, p-chloromercuribenzoate (PCMB), L-ascorbic acid, melibiose, stachyose, and D-galactose. Also the purified enzyme showed a lectin activity with trypsinized erythrocytes.
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PMID:Purification and properties of alpha-galactosidase from immature stalks of Saccharum officinarum (sugar cane). 627 79

Particles of meconium sedimenting at 105,000 g contain sucrase and various brush border peptidase activities. Oligoaminopeptidase, dipeptidylaminopeptidase, and sucrase solubilized by papain from meconium particles of preterm newborns or from brush border of human fetuses during the 4th month of gestation were compared with the same enzymes prepared from adult jejunal and ileal brush border. The following are characteristics of fetal intestinal brush border enzymes: (a) a faster anodal electrophoretic mobility in polyacrylamide and in agar gel; (b) the same specific activity, as measured by quantitative crossed immunoelectrophoresis utilizing an antiserum against adult brush border membranes; (c) complete fusion of the immunoprecipitation lines with the adult enzymes by using the same antiserum; and (d) a different binding pattern to Helix pomatia lectin and lentil lectin. The results suggest that the charge difference between adult and fetal human brush border enzymes, which causes the difference in the gel electrophoretic mobility, is most probably due, at least in part, to differences in carbohydrate composition of these glycoproteins. Extensive neuraminidase digestion causes no or only minor changes of the electrophoretic mobility of the meconial enzymes. The difference between adult and meconial enzymes is therefore apparently not, or not only, due to different sialic acid content. These results suggest that many intestinal brush border enzymes in fetal life and at birth are in forms structurally different from those in adult life.
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PMID:Fetal forms of oligoaminopeptidase, dipeptidylaminopeptidase IV, and sucrase in human intestine and meconium. 636 65

Mannose-specific binding sites for horseradish peroxidase (HRP) were studied in paraformaldehyde-fixed, frozen sections of endocrine organs by a cytochemical method reported previously. In the testis, HRP was bound to interstitial cells, probably macrophages, and to sites extending along the surface of spermatozoa in the seminiferous tubules. In the epididymis, cells in the connective tissue, probably fibroblasts or macrophages, showed the specific reaction. In the ovaries, the reaction for lectin-bound HRP was observed in connective tissue cells of the theca externa, and in the mucosa of the uterus, binding of HRP occurred to many fibroblasts. The glycoprotein was also bound to cells in the connective tissue of the thyroid, probably mast cells, as well as to endothelial cells in the adrenal medulla and cortex. In all cases, the binding reaction required Ca2+ and was suppressed by mannose or mannan. Partially purified and highly purified preparations of glycoprotein hormones [ovine follicle-stimulating hormone, ovine luteinizing hormone, bovine thyroid-stimulating hormone, and human chorionic gonadotropin] as well as bovine thyroglobulin and yeast invertase competed with the binding of HRP to all the cells mentioned thus showing that the hormones were bound to the same sites as HRP. When 1 microM HRP was present in the incubation medium, the addition of 15-25 microM of highly purified hormones almost suppressed the reaction for lectin-bound HRP and competitive effects could be observed at even lower concentrations of the hormones.
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PMID:Competition between glycoprotein hormones and horseradish peroxidase for mannose-specific binding sites in cells of endocrine organs. 688 15

The intramembranous particles of yeast Saccharomyces cereisiae plasma membrane form paracrystalline arrays or are randomly distributed as seen by freeze-fracture electron microscopy. Protoplasts with randomly distributed particles and with paracrystalline arrays were isolated and subsequently labeled with 3H-Con A, Con A and ferritin-Con A. The distribution of the Con A or the ferritin-Con A molecules on deep-etched exoplasmic surfaces strongly resembled the distribution of the intramembranous particles. The influence upon labeling of buffer ionic strength was investigated. Binding assays with 3H-Con A and freeze-etch electron microscopy demonstrated that the amount of non-specifically bound lectin molecules decreases by increasing buffer ionic strength. Only partial removal of Con A molecules was achieved by adding various concentrations of the specific sugar Methyl-alpha-D-Mannoside (alpha MM) to labeled protoplasts. By means of analytical ultracentrifugation it was found that alpha MM also promotes the formation of Con A dimers. fixed protoplasts were treated with detergents and 2-chloroethanol at various concentrations and subsequently labeled with 3H-Con A or ferritin-Con A. The amount of Con A bound to extracted cells did not decrease but ultrastructural changes of the deep-etched surfaces were observed. From our data it can be concluded that only the glycoproteins are labeled with Con A and they seem to be associated with the intramembranous particles [15]. Each intramembranous particle seems to bind 36 to 44 Con A molecules and therefore the glycoproteins seem to possess very long sugar chains. This further supports the hypothesis that the intramembranous particles are associated with the membrane-bound invertase.
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PMID:Specific labeling of glycoproteins in yeast plasma membrane with concanavalin A. 702 44

The effect of concanavalin A on biosynthesis of nucleic acids, proteins, structural polysaccharides and glycoproteins of the yeast cell membrane and of enzymes having different localization in the cell as well as on other processes occurring in spheroplasts of the yeasts Saccharomyces cerevisiae IBPhM-350 and CCY 21-4-13 were studied. In both yeast strains lectin strongly inhibited total protein synthesis and produced a weaker inhibiting effect on DNA and RNA synthesis. This was accompanied by a decrease of the activity of the majority of already known enzymes (acid phosphatase, invertase, alpha-glucosidase, polyphosphatase, pyrophosphatase, ATPase) and glucose consumption. In addition concanavalin A inhibited the synthesis of structural components of the yeast cell membrane, i.e. mannane and glucane. The data obtained suggest that lectin (50 microgram/ml or higher) has a toxic effect on yeast spheroplasts (or protoplasts).
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PMID:[Inhibiting effect of concanavalin A on certain biosynthetic processes in spheroplasts of the yeast Saccharomyces cerevisiae]. 705 45

Invertase from Baker's yeast (Saccharomyces cerevisiae) and Horseradish peroxidase (HRP) were covalently immobilized on Concanavalin A precoupled to Seralose via carbohydrate moieties. Covalent coupling of glycoenzymes was achieved by periodate induced aldehydic groups of glycosyls with amino groups of Concanavalin A, at different pH values. A bifunctional reagent such as glutaraldehyde crosslinks the glycoenzymes with lectin both intra and intermolecularly. Therefore, attempts were made to introduce covalent linkages between glycoenzymes and Concanavalin A-Seralose without intramolecular crosslinking in either. The immobilized preparations of glycoenzymes exhibited high yield of immobilization and eta value. About 90 and 85% covalent coupling could be observed in invertase and HRP at pH 7.0 respectively, as determined by treatment with 0.5 M methyl alpha-D-mannopyranoside. All immobilized glycoenzyme preparations exhibited marked stabilization towards thermal inactivation.
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PMID:Covalent immobilization of invertase and horseradish peroxidase on concanavalin A-Seralose via carbohydrate moieties. 754 67

A method for analysing microgram amounts of microvillar membranes by two-dimensional electrophoresis (protein mapping) is described, and has been used to characterize the microvillar proteins of the small intestine of German shepherd, corgi, and beagle dogs. Detergent-solubilized microvillar membranes were radiolabelled with 14C and separated by isoelectric focussing followed by SDS-PAGE. Proteins were detected fluorographically and glycoproteins by lectin-affinity staining. The microvillar hydrolases alkaline phosphatase and dipeptidyl aminopeptidase IV were identified by active-site labelling and aminopeptidase N by immunoprecipitation. Changes following pancreatic duct diversion were consistent with accumulation of pro-sucrase-isomaltase and diminished expression of the sucrase and isomaltase subunits. Cytoskeletal proteins were concentrated in the core fraction remaining after extraction of microvillar membranes with Triton X-100. There were no consistent differences between dogs of different breed, and the canine protein maps were similar to the human.
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PMID:Characterization of microvillar membrane proteins of dog small intestine by two-dimensional electrophoresis. 758 24

Three different classes of signals for plant vacuolar targeting have been defined. Previous work has demonstrated that the carboxyl-terminal propeptide (CTPP) of barley lectin (BL) is a vacuolar targeting signal in tobacco plants. When a mutant BL protein lacking the CTPP is expressed in tobacco, the protein is secreted. In an effort to determine the universality of this signal, the CTPP was tested for its ability to target proteins to the vacuole of Saccharomyces cerevisiae. Genes encoding fusion proteins between the yeast secreted protein invertase and BL domains were synthesized and transformed into an invertase deletion mutant of yeast. Invertase assays on intact and detergent-solubilized cells demonstrated that invertase+CTPP was secreted, while nearly 90% of the invertase::BL+CTPP (fusion protein between invertase and BL containing the CTPP) and invertase::BL-CTPP proteins (fusion between invertase and BL lacking the CTPP) were retained intracellularly. These fusions were secreted in a mutant of yeast that normally secretes proteins targeted to the vacuole. With this and previous work, proteins representing all three classes of plant vacuolar targeting signals have now been tested in yeast, and in all cases, the experiments indicate that the plant proteins are directed to the yeast vacuole using signals other than those recognized by plants.
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PMID:A carboxy-terminal plant vacuolar targeting signal is not recognized by yeast. 792 Jul 13


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