Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endogeneous hyperglucagonemia is observed in experimental diabetes mellitus and semistarvation, conditions associated with an increased intestinal absorptive function. To examine whether glucagon might exert a similar adaptive response on intestinal digestive-absorptive function like experimental diabetes mellitus the effect of chronic glucagon administration on intestinal transport of 3-0-methyl-D-glucose, water, sodium, potassium, and D-glucose induced transmural potential difference (PD) was examined by an in vivo perfusion technique in rat small intestine. Chronic administration of glucagon (100 mug twice daily) for 5 days resulted in increased absorption of 3-0-methyl-D-glucose, water, sodium and potassium as well as in an increase of D-glucose induced PD. A similar, but more pronounced augmentation of D-glucose induced PD was observed in the jejunum of streptozotocin-diabetic rats. Disaccharidase (maltase, sucrase, trehalase, lactase) and alkaline phosphatase activities were not affected in intestinal mucosa of glucagon-treated rats compared to controls. It cannot be decided from these results whether hyperglucagonemia is responsible for the adaptive intestinal changes observed in experimental diabetes mellitus.
 ...
PMID:Effect of chronic glucagon-administration on the digestive and absorptive function of rat small intestine in vivo. 98 1

Yeast external invertase (EC 3.2.1.25), a glycoenzyme consisting of equal parts by weight of protein and mannan, has been found to contain covalently bound phosphate. Three preparations (from two yeast strains) had mannose/PO4 ratios of 31-35, equivalent to 24-27 PO4 residues per mol of enzyme, while a fourth had only 7 PO4 residues per mol. From one of the high-PO4 enzymes, approx. 69% of the phosphorus was recovered as mannose 6-phosphate. No correlation was found between invertase activity and phosphorus content. The PO4 contents of the invertases exceeded those of the cell wall mannans from the respective yeasts. Thus, contamination of the invertases by cell wall phosphomannan is unlikely. Electrofocusing of the low-PO4 invertase yielded four components with pI values from 3.96 to 4.40, and yeast internal invertase (a mannan- and PO4-free, cytoplasmic isozyme) was isoelectric at approx. pH 4.5. The high-PO4 invertase was considerably more heterogeneous, with two major species of pI 3.65 and 3.32 and a highly acidic component of pI smaller than 2.7; however, the mannose/PO4 ratio of each species was approximately the same. PO4-gradient elution from hydroxyapatite resolved the high-PO4 invertase into five isozymes of increasing acidity and mannan content. Since the mannose/PO4 ratios of these invertase species are constant, the increase in the mannan/protein (and, therefore PO4/protein ratio is apparently responsible for the microheterogeneity of phosphoinvertase.23
 ...
PMID:Microheterogeneity in yeast invertase. 109 60

The mechanism of inhibition by 2-deoxy-D-glucose of the synthesis of yeast wall polysaccharides and glycoproteins was investigated in Saccharomyces cerevisiae cells and protoplasts. The extent of the inhibition of mannan and glucan synthesis was found to be dependent on whether glucose or mannose was used as the carbon source in the medium. During growth on glucose, 2-deoxy-D-glucose inhibited more intensively mannan than glucan formation. Biosynthesis of wall glucan was strongly suppressed in mannose medium. Selective incorporation of 2-deoxy-D-glucose occurred into that polysaccharide, synthesis of which was more inhibited under given conditions. Suggestive evidence has been obtained that the decisive factor for the proportion of glucan and mannan in the walls is the direction of glucose 6-phosphate/mannose 6-phosphate interconversion dependent on the exogeneous hexose. No close correlation was found between the inhibition of mannan synthesis and the appearance of the mannan-protein enzymes invertase and acid phosphatase. Effect of 2-deoxy-D-glucose was therefore investigated on the parallel synthesis of protein, mannan and several extracellular and intracellular enzymes in protoplasts grown on glucose and mannose. The results obtained pointed out that the hindrance of the secretion of mannan-protein enzymes is of a complex nature and related more to the inhibition of synthesis of the protein moiety than to the inhibition of glycosylation. Synthesis of several enzymes was found to be a subject of a metabolic control by 2-deoxy-D-glucose or its metabolites.
 ...
PMID:Mechanism of 2-deoxy-D-glucose inhibition of cell-wall polysaccharide and glycoprotein biosyntheses in Saccharomyces cerevisiae. 110 Mar 78

The molecular forms of yeast invertase have been studied. It is shown that by gel filtration on Sephadex G-200 it is possible to demonstrate the presence not only of a light, carbohydrate-free, invertase, and a heavy invertase containing 50% carbohydrate, but also of a continuous spectrum of molecular forms that probably represent the sequential addition of mannose to the light form during the secretion process, which culminates in the formation on the heavy enzyme that is found outside the cytoplasmic membrane. The elution volume-void volume ratio in Sephadex G-200 varies from 1.75 of the light to 1.05 of the heavy invertase. The separation of invertase has also been achieved by ion-exchange chromatography and by isoelectric focusing and is facilitated by removal of the heavy form by ammonium sulphate precipitation. During the protoplasting process the removal of the cell wall is accompanied by the loss of most of the heavy form. Thintermediate forms are exclusively detected inside the protoplast, together with the light invertase and a small amount of heavy invertase. The effect of 2-deoxy-D-glucose and cycloheximide on the biosynthesis and distribution of molecular forms of yeast invertase has also been studied. In the presence of 10 mM glucose Saccharomyces 303-67 repressed cells readily synthesize invertase during the two-hour incubation period. Upon the addition of 2-deoxy-D-glucose, at a concentration of 75 mu g/ml, the observed inhibition in the cells is 60%, but if the activity is measured after breaking the cells, only a 31% inhibition is found, revealing an accumulation of invertase inside the protoplast. 2-Deoxy-D-glucose originates a pile-up of the light and intermediate forms at the expense of the formation of the heavy enzyme, showing that the inhibition of the glycosilation and, therefore, the secretion process, has taken place. In the absence of de novo invertase synthesis originated by cycloheximide, the glycosilation process still takes place as indicated by the accumulation of the heavy form at the expense of the light, carbohydrate-free, enzyme.
 ...
PMID:Molecular forms of yeast invertase. 111 70

The synthesis of beta-glucanase either by cells or by protoplasts of the yeast Pichia polymorpha has been found to occur in the presence of 2-deoxy-D-glucose in the growth medium. On the other hand, the synthesis of typical extracellular proteins such as invertase and acid phosphatase is strongly affected by the presence of the drug. The degree of inhibition is, however, directly related to the 2-deoxy-D-glucose concentration.
 ...
PMID:Synthesis of beta-glucanase and other extracellular proteins by cells and protoplasts of the yeast Pichia polymorpha: effect of 2-deoxy-D-glucose. 119 Sep 60

We compared the receptor-mediated endocytosis for galactose and mannose exposing ligands in primary cultures of hepatocytes from newborn and adult rats. The endocytic pathway was revealed ultrastructurally using colloidal gold particles coupled to lactosylated bovine serum albumin and invertase. The binding activity on the cell surfaces is observed by keeping the cells at 4 degrees C. For both ligands used, the binding capacity for hepatocytes from adult rats was greater than for neonatal cultured cells. Increasing the temperature to 37 degrees C, we observed that the protein-gold complexes entered the intracellular endocytic organelles. Within 5-15 min, the marker was confined in vesicles close to the cell surface and in the endosome, while after 60 min, the marker is found in lysosome-like compartments. We found that the process of endocytosis is similar for galactose and mannose exposing ligands. The organelles involved in the process of endocytosis in newborn cultured hepatocytes are not different in shape from those of cultured cells of adult rats, but the process of internalization is slower.
 ...
PMID:Receptor-mediated endocytosis of galactose and mannose exposing ligands: an electron microscopic study on adult and neonatal cultured rat hepatocytes. 131 31

In this study, glucose repression in Saccharomyces cerevisiae was analysed under defined physiological conditions, at both the molecular and physiological levels, by pulsing glucose to a galactose-limited continuous culture. During this pulse of glucose, the galactose feed was kept constant. Directly after the glucose pulse, carbon dioxide production increased while oxygen consumption remained constant, demonstrating that the surplus of glucose had been consumed by means of fermentation. The direct accumulation of galactose in the medium after the glucose pulse indicated that the consumption of galactose had been stopped instantaneously. Galactose uptake experiments revealed that the galactose transporter was still present but apparently was incapable of galactose uptake, which could be due to inhibition of the galactose transporter by glucose. The total concentration of cAMP increased from 5 nmol g-1 at t = 0 to 25 nmol g-1 at t = 1.5 min. After 2 min the concentration of cAMP gradually decreased again to the normal level. Within 2 min after the addition of glucose, the transcription of the GAL genes and SUC2 was inhibited. In addition, the transcription of the HXK1 gene, encoding hexokinase isoenzyme 1, was also inhibited, which demonstrates that the HXK1 gene is regulated at the transcriptional level comparable with invertase.
 ...
PMID:Analysis of glucose repression in Saccharomyces cerevisiae by pulsing glucose to a galactose-limited continuous culture. 133 40

Ethanol feeding to rats for 40 days enhanced (p < 0.001) the activities of alkaline phosphatase, sucrase, gamma-glutamyltransferase (GTP), and p-nitrophenyl (PNP)-beta-D-galactosidase (p < 0.05) with no change in leucine amino peptidase (LAP) and PNP-beta-D-glucosidase activities in intestine compared with control rats. The activities of alkaline phosphatase, sucrase, and GTP were diminished (p < 0.01) in ethanol-fed malnourished rats. There was no change in LAP activity, but the levels of glucosidase and galactosidase were elevated under these conditions. Brush-border sialic acid, fucose, hexose, and hexosamine contents were elevated in ethanol-fed protein-deficient animals. Ethanol administration to normally fed rats elevated the membrane sialic acid and hexose contents, reduced fucose content, and had no effect on brush-border hexosamine content compared with the control group. These results are in agreement with data on lectin binding to brush borders under these conditions. Alcohol ingestion reduced the incorporation of [14C]-glucosamine into brush borders in rats maintained on an 18% protein diet but augmented the incorporation of [14C]-glucosamine and [14C]-mannose in protein-malnourished membranes. These observations suggest that nutrition status influences the sensitivity of microvillus membrane glycosylation to ethanol feeding in rat intestine.
 ...
PMID:Chronic ethanol feeding and microvillus membrane glycosylation in normal and protein-malnourished rat intestine. 142 85

Nicarbazin is an anticoccidial drug, used mainly in birds, which has shown several other effects including inhibition of growth and feed efficiency in poultry, and stimulation of sugar and amino acid intestinal absorption in rabbit. The present work was designed to determine whether nicarbazin added to the feed, affects growth and feed intake in rabbit, and whether the continuous ingestion of nicarbazin can alter the mechanisms of intestinal nutrient absorption or digestion in this species. Nicarbazin, administered at the recommended dose (125 ppm) had no harmful effects either on growth or on feed intake of animals. After treatment for one month with nicarbazin at the dose of 125 ppm added to the feed, rabbits displayed a higher transport ability of both D-glucose and L-leucine through the enterocyte plasma membranes than did untreated rabbits. These animals also showed higher specific activities of two brush-border enzymes, sucrase and aminopeptidase N, than the control animals.
 ...
PMID:Effects of nicarbazin on intestinal digestion and absorption of nutrients in the rabbit. 136 52

During refolding and reassociation of chemically denatured non-glycosylated invertase from Saccharomyces cerevisiae, aggregation competes with correct folding, leading to low yields of reactivation (Kern et al. (1992) Protein Sci. 1, 120-131). In the presence of the chaperone GroEL, refolding is completely arrested. This suggests the formation of a stable complex between GroEL and non-native non-glycosylated invertase. Addition of MgATP results in a slow release of active invertase from the chaperone complex. When GroEL/ES and MgATP are present during refolding, the final reactivation yield increases from 14% to 36%. In contrast, refolding of the core-glycosylated and the high-mannose glycosylated forms of invertase is not arrested by GroEL. Only a short lag phase at the beginning of reactivation and a slightly increased reactivation yield (64% to 86% for core-glycosylated and 62% to 76% for external invertase) indicate a weak interaction of the glycosylated forms with the chaperone.
 ...
PMID:Glycosylation inhibits the interaction of invertase with the chaperone GroEL. 136 29


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>