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)

Gluten withdrawal from the diet is occasionally used speculatively in the management of multiple sclerosis. To assess whether there might be any rational basis for such a measure we have undertaken morphological and biochemical studies of the jejunal mucosa in 14 patients with multiple sclerosis. All were found to have morphologically normal villi, and quantitative estimation of surface-to-volume ratios gave values which did not differ from control subjects. Intraepithelial lymphocyte counts were normal. Antigliadin antibody titres were not raised in any patient. Estimation of activity of the brush border disaccharidases (sucrase, lactase, and maltase (showed that the mean level of each enzyme did not differ significantly from control subjects. Analytical subcellular fractionation of the biopsies showed no changes in the distribution or activity of marker enzymes for the brush order, lysosomes, mitochondria, cytosol, peroxisomes, or endoplasmic reticulum. It is concluded that there are no gross morphological or biochemical abnormalities in the jejunal mucosa in patients with multiple sclerosis and, therefore, that the use of gluten-free diets cannot be justified on the assumption that these patients suffer from a coeliac-like lesion of the small intestine.
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PMID:Morphological and biochemical findings in jejunal biopsies from patients with multiple sclerosis. 44 78

Absorption of 57Co-labelled vitamin B12 - intrinsic factor (IF) complex and its binding to mucosal precipitate and brush border fractions of rat small intestine was studied in rats pair-fed with a liquid diet containing ethanol 5 g/100 ml, 35% of calories, or isocalorically substituted sucrose. IF was obtained from rats fasted for 18 h. and for each experiment the amount of vitamin B12 added was the minimum required to achieve maximum binding to IF. Rats fed alcohol exhibited hepatic steatosis, proliferation of smooth endoplasmic reticulum, and disordered mitochondria after 6 weeks on the diet, and absorption of vitamin B12, fed with IF by stomach tube, was reduced signficantly. In contrast, binding of 57Co-labelled vitamin B12 -IF complex to mucosal precipitate and brush border fractions was never less than that of fractions from control rats at 4, 8 and 12 weeks on the alcohol diet. Furthermore, binding to the brush border was significantly greater in alcohol-fed rats at 12 weeks whether expressed per unit of beta-naphthylamidase (EC 3.4.1.1) activity or per milligram of protein. Total mucosal sucrase (EC 5.2.1.26) and beta-naphthylamidase were unchanged or slightly increased (beta-naphthylamidase at 12 weeks) on the alcohol-containing diet indicating that total brush border membrane was not reduced. Total brush border binding activity was the same in alcohol-fed and control rats at each time period. These results indicate that malabsorption of vitamin B12 in rats fed alcohol cannot be due to decreased binding of the vitamin B12 - IF complex by brush border membrane receptors, or secondary to a net decrease in membrane receptors.
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PMID:Lack of effect of alcohol on small intestinal binding of the vitamin B12 - intrinsic factor complex. 97 75

The role of carbohydrate chains for the structure, function, stability, and folding of glycoproteins has been investigated using invertase as a model. The protein is encoded by several different genes, and its carbohydrate moiety is heterogeneous. Both properties complicate physicochemical comparisons. Here we used the temperature-sensitive sec18 secretion mutant of yeast with a single invertase gene (SUC2). This mutant produces the carbohydrate-free internal invertase, the core-glycosylated form, and, at the permissive temperature, the fully glycosylated external enzyme, all with identical protein moieties. The core-glycosylated enzyme resembles the nascent glycoprotein chain that folds in the endoplasmic reticulum. Therefore, it may be considered a model for the in vivo folding of glycoproteins. In addition, because of its uniform glycosylation, it can be used to investigate the state of association of native invertase. Glycosylation is found to stabilize the protein with respect to thermal denaturation and chaotropic solvent components; the stabilizing effect does not differ for the external and the core-glycosylated forms. Unlike the internal enzyme, the glycosylated forms are protected from aggregation. Native internal invertase is a dimer (115 kDa) whereas the core-glycosylated enzyme is a mixture of dimers, tetramers, and octamers. This implies that core-glycosylation is necessary for oligomerization to tetramers and octamers. Dimerization is required and sufficient to generate enzymatic activity; further association does not alter the specific activity of core-glycosylated invertase, suggesting that the active sites of invertase are not affected by the association of the dimeric units. Reconstitution of the glycosylated and nonglycosylated forms of the enzyme after preceding guanidine denaturation depends on protein concentration. The maximum yield (approximately 80%) is obtained at pH 6-8 and protein concentrations < or = 4 micrograms/mL for the nonglycosylated and < or = 40 for the glycosylated forms of the enzyme. The lower stability of the internal enzyme is reflected by a narrower pH range of reactivation and enhanced aggregation. As indicated by the sigmoidal reactivation kinetics at low protein concentration both folding and association are rate-determining.
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PMID:Stability, quaternary structure, and folding of internal, external, and core-glycosylated invertase from yeast. 130 75

Fed and fasted (18 h) adult male rats received a primed constant infusion of [3H]leucine for 15 to 180 min. Prosucrase-isomaltase (pro-SI) and sucrase were isolated from mixed jejunal mucosal membranes by immunoprecipitation and separated from one another by polyacrylamide gel electrophoresis under denaturing and reducing conditions. The rate at which pro-SI was processed to sucrase was calculated on the assumption that the steady-state specific radioactivity of leucine in pro-SI defined the pool of amino acids used in the formation of brush border sucrase. At isotopic steady state, pro-SI achieved a specific radioactivity that was higher than that of mucosal free leucine in both feeding groups. The relationship between the isotopic equilibrium of the free amino acid pools and pro-SI was sensitive to feeding status; the specific radioactivity of pro-SI was 25 and 55% (P less than 0.05) of the blood specific radioactivity in fed and fasted animals, respectively. The fractional rate of pro-SI processing tended to be higher (P less than 0.07) in fed (407%/d) than in fasted animals (274%/d). We conclude that the general mucosal free amino acid pool is not the amino acid pool from which pro-SI is synthesized and that the rate of pro-SI processing from the endoplasmic reticulum-Golgi membranes to the brush border membrane is sensitive to the feeding status of the animal.
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PMID:Feeding status affects in vivo prosucrase.isomaltase processing in rat jejunum. 154 10

Previously, Man8-14GlcNAc oligosaccharides were isolated from highly purified Saccharomyces cerevisiae invertase and shown by one-dimensional 1H NMR spectroscopy and alpha 1,2-linkage-specific mannosidase digestion to constitute a homologous series of nearly homogeneous compounds, which appeared to define the intermediates in oligosaccharide core synthesis in yeast (Trimble, R.B. and Atkinson, P.H. (1986) J. Biol. Chem., 261, 9815-9824). To evaluate whether invertase oligosaccharides reflected global core processing of yeast glycans, the soluble glycoprotein pool of disrupted log-phase cells was digested with endo-beta-N-acetyl-glucosaminidase H and Man8-13GlcNAc were isolated by Bio-Gel P-4 chromatography. Although analysis of each size class by one-dimensional 400 MHz and two-dimensional 500 MHz phase-sensitive COSY 1H NMR spectroscopy revealed considerable structural heterogeneity in all but Man8GlcNAc, the major positional isomer in Man9-13GlcNAc (approximately 50%) was identical to that previously elucidated on invertase. The heterogeneity resided in four families of oligosaccharides: (i) Glc3Man9GlcNAc----Man8 GlcNAc trimming intermediates; (ii) alpha-mannosidase degradation products of the principal isomers; (iii) mannan elongation intermediates; (iv) core structures with the alpha 1,2-linked mannose usually removed by the processing alpha-mannosidase. The potential for the vacuolar alpha-mannosidase (AMS1 gene product) to generate heterogeneity in vitro was confirmed by isolating oligosaccharides from AMS1 and ams1 yeast strains in the presence of a Man13GlcNAc[3H]-ol marker (where GlcNAc[3H]-ol is N-acetylglucosamin [1-3H]itol). Degradation of the Man13GlcNAc[3H]-ol to Man9-12GlcNAc[3H]-ol occurred in the former, but not in the latter. A role for the vacuolar alpha-mannosidase in generating at least some heterogeneity in vivo was inferred from the 1H NMR spectrum of the AMS1 Man11GlcNAc pool, which showed more structural isomerism than seen in the spectrum of a comparable ams1 Man11GlcNAc preparation. Thus, the principal biosynthetic pathway of inner core mannan in Saccharomyces is defined by the Man8-13GlcNAc oligosaccharides found on external invertase, while structural heterogeneity in these size classes results from precursor processing in the endoplasmic reticulum, core extension in the Golgi and metabolic degradation in the vacuole.
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PMID:Structural heterogeneity in the Man8-13GlcNAc oligosaccharides from log-phase Saccharomyces yeast: a one- and two-dimensional 1H NMR spectroscopic study. 155 Sep 91

We have analyzed a series of Moloney murine leukemia (M-MuLV) envelope (env) protein fusions to the marker proteins invertase and placental alkaline phosphatase (PLAP), expressed in Psi2 retrovirus packaging cells. The yeast invertase protein, fused at its third amino acid residue to the amino-terminal signal sequence and 17 residues of the mature M-MuLV env protein, retained its enzymatic activity and was secreted from mammalian cells. However, env protein fusions to the C-terminal portion of invertase were inactive. In contrast, some, but not all, env protein fusions at the C-terminal region of PLAP were enzymatically active: PLAP fusions containing long C-terminal portions of env localized to the rough endoplasmic reticulum (RER) and possessed low enzyme activity levels, while fusion constructs containing relatively short portions of the M-MuLV env gene localized to the Golgi and had higher activity levels. Those proteins that localized to the Golgi also were processed, in part, to forms of 67 to 68 kDa, the size of the mature PLAP protein. Since PLAP ordinarily is transferred to a phosphatidyl-inositol glycan tail (PIG-tail) in the Golgi and then transported to the plasma membrane, it appears that Golgi-localized PLAP-env fusions are processed imperfectly. PLAP itself, when expressed in Psi2 cells, accumulated at the plasma membrane and, unlike the PIG-tailed Thy-1 protein, was not incorporated into virus particles. Thus, the reported incorporation of the Thy-1 protein into M-MuLV virions does not appear to be a consequence of its glycoprotein tail.
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PMID:Retroviral envelope protein fusions to secreted and membrane markers. 158 54

Four yeast secretion signals, the 19-amino-acid invertase signal sequence, the 17-amino-acid acid-phosphatase signal sequence, and the pre-sequence and prepro-sequence of prepro-alpha-factor have been used to look for the secretion of recombinant human insulin-like growth factor 1 (IGF1) from Saccharomyces cerevisiae. Only the prepro-sequence, often referred to as the alpha-factor leader and consisting of an N-terminal 19-amino-acid pre-sequence or signal sequence attached to a 66-amino-acid pro-region, permits secretion of IGF1. The signal sequences alone do not allow the translocation of IGF1 into the endoplasmic reticulum. This is evident from the fact that IGF1-like molecules, to which the signal sequences are still attached, accumulate intracellularly in the cytosol. Fusion of the pro-region of the alpha-factor leader to the C-terminus of the acid-phosphatase and invertase signal sequences allows IGF1 to be secreted once again. These results reveal the essential role of the pro-region of the alpha-factor leader in the secretion of IGF1 and indicate that it may have a function in guiding a nascent IGF1 polypeptide to a state in which translocation can occur.
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PMID:The pro-region of the yeast prepro-alpha-factor is essential for membrane translocation of human insulin-like growth factor 1 in vivo. 160 61

The function of the SRH1 product, the yeast homologue of the 54 kDa subunit of the mammalian signal recognition particle, has been analyzed using a galactose dependent mutant of the gene. SRH1 has been placed under control of the GAL1 promoter and introduced into a haploid cell that had its chromosomal SRH1 copy disrupted. This mutant grows normally on galactose medium but slows down the growth about 10 h after transfer to glucose medium. At the same time, precursor forms of secretory proteins, alpha-mating factor and invertase, accumulate in the cells. This result indicates that the SRH1 product is involved in translocation of precursors of secretory proteins across the endoplasmic reticulum membrane in yeast cells.
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PMID:SRH1 protein, the yeast homologue of the 54 kDa subunit of signal recognition particle, is involved in ER translocation of secretory proteins. 164 26

To investigate the role and mechanism of action of epidermal growth factor (EGF) in the intestinal epithelium, we have studied its influence on proliferation and differentiation of Caco-2 cells, a human colon adenocarcinoma cell line exhibiting several characteristics of adult small intestinal enterocytes. A clone of Caco-2 cells synthesizing minimal amounts of transforming growth factor-alpha (TGF-alpha)/epidermal growth factor (EGF)-like activity was used in these studies. Cells grown in the presence of 20-200 ng EGF/ml exhibited increased DNA synthesis and proliferation; formation of morphologically poorly differentiated multilayers was observed at 200 ng EGF/ml. At all concentrations tested EGF produced a significant and marked reduction in sucrase activity, whereas other brush-border enzymes (aminopeptidase N, alkaline phosphatase, dipeptidylpeptidase IV) were only marginally affected. EGF influenced sucrase expression at two different levels. At 20 ng/ml, it affected primarily sucrase-isomaltase processing in the endoplasmic reticulum and/or increased its degradation. At 200 ng EGF/ml, a significant and marked reduction in sucrase-isomaltase mRNA levels and biosynthesis was observed. These results demonstrated that EGF has important and selective effects on Caco-2 cell proliferation and differentiation and may affect different cellular activities depending on its concentration.
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PMID:Inhibition of sucrose-isomaltase expression by EGF in the human colon adenocarcinoma cells Caco-2. 176 18

The ERG9 gene of Saccharomyces cerevisiae has been cloned by complementation of the erg9-1 mutation which affects squalene synthetase. From the 5 kb insert isolated, the functional gene has been localized on a DNA fragment of 2.5 kb. The presence of squalene synthetase activity in E. coli bearing the yeast DNA fragment isolated, indicates that the structural gene encoding squalene synthetase has been cloned. The sequence of the 2.5 kb fragment contains an open reading frame which could encode a protein of 444 amino acids with a deduced relative molecular mass of 51,600. The amino acid sequence reveals one to four potential transmembrane domains with a hydrophobic segment in the C-terminal region. The N-terminus of the deduced protein strongly resembles the signal sequence of yeast invertase suggesting a specific mechanism of integration into the membranes of the endoplasmic reticulum.
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PMID:Isolation and primary structure of the ERG9 gene of Saccharomyces cerevisiae encoding squalene synthetase. 180 26


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