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:3.2.1.20 (alpha-glucosidase)
4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 6-O-butanoyl derivative of castanospermine (MDL 28,574: BUCAST), an inhibitor of glycoprotein processing, blocked the growth of herpes simplex virus type-2 with the effect markedly enhanced by exposure of cells to the compound pre- as well as post-infection. The effectiveness of the derivative corresponded to an increased uptake with greatest accumulation after virus infection. Gas chromatography/mass spectrometry identified the predominant component in MDL 28,574 treated cells as castanospermine, an inhibitor of alpha-glucosidase 1. The effects of this compound on the synthesis of viral glycoprotein, gB, was determined with the increased molecular weight of the mannose-rich precursor evidence for the modulation of glycoprotein processing.
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PMID:Antiviral activity and metabolism of the castanospermine derivative MDL 28,574, in cells infected with herpes simplex virus type 2. 788 39

We have investigated the autophagocytic process of excess peroxisomes and mitochondria induced by di-(2-ethylhexyl)phthalate (DEHP) treatment using immunocytochemical techniques. Rat liver peroxisomes were induced by 2 weeks treatment with DEHP. The animals were then injected with leupeptin (2 mg/100 g body weight), and their livers were fixed by perfusion at various intervals. The liver tissues were embedded in LR White or Epon. Semithin sections of the Epon-embedded tissue were stained for cathepsin D, B, and H, and lysosomal glycoprotein (LGP107) by the immunoenzyme technique after removal of epoxy resin. Thin sections of LR White-embedded tissue were stained for the same antigens by the immunogold technique. Some liver specimens were processed to ultracryotomy, and frozen-thawed thin sections were immunostained for carboxylesterase E1 and alpha-glucosidase II, endoplasmic reticulum (ER) markers. Twenty minutes after leupeptin injection, many peroxisomes and mitochondria were surrounded by a double-layered membrane (isolation membrane) continuous with the ER. These membranes were positive for carboxylesterase E1 and alpha-glucosidase, but not for LGP107 as well as cathepsins. Forty to 60 minutes after leupeptin injection many autophagic vacuoles showing various developing stages appeared and accumulated. The early autophagic vacuoles were surrounded by a double-layered membrane, whereas the late autophagic vacuoles had a single limiting membrane. The former was negative for cathepsins as well as LGP107, but positive for carboxylesterase E1 and alpha-glucosidase II. The results suggest strongly that the isolation membrane is derived from the ER membrane and converted later into the lysosomal membrane and support our previous morphological observations.
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PMID:Formation of autophagosomes during degradation of excess peroxisomes induced by di-(2-ethylhexyl)phthalate treatment. II. Immunocytochemical analysis of early and late autophagosomes. 792 93

The 6-O-butanoyl derivative of castanospermine (MDL 28,574) was previously shown to be approximately 30-fold more potent than the naturally occurring molecule at inhibiting the replication of human immunodeficiency virus (HIV) (D. L. Taylor, P. S. Sunkara, P. S. Liu, M. S. Kang, T. L. Bowlin, and A. S. Tyms, AIDS 5:693-698, 1991). We now report that consistent with its improved anti-HIV activity, MDL 28,574 is more effective (50% inhibitory concentration [IC50], 20 microM) than the parent molecule (IC50, 254 microM) at causing the accumulation of glucosylated oligosaccharides in HIV-infected cells by inhibition of glycoprotein processing. These were predominantly of the glucose 3 type, as determined by P4 Bio-Gel analysis after digestion with purified alpha-glucosidase I, indicating that, intracellularly, this enzyme is the major target for inhibition. MDL 28,574, however, was less active (IC50, 1.27 microM) than castanospermine (IC50, 0.12 microM) against the mutual target enzyme, cellular alpha-glucosidase I, in a cell-free assay system. The increased effects of MDL 28,574 against alpha-glucosidase I in cell culture were attributed to the improved cellular uptake of the more lipophilic derivative. Inhibition of this enzyme activity in HIV-infected H9 cells impaired viral glycoprotein processing and resulted in the expression of abnormally configured gp120. This did not affect virus production, but the virions had decreased infectivity which was partially related to a reduced ability to bind to CD4+ T cells.
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PMID:Inhibition of alpha-glucosidase I of the glycoprotein-processing enzymes by 6-O-butanoyl castanospermine (MDL 28,574) and its consequences in human immunodeficiency virus-infected T cells. 798 8

Mobilization of Ca2+ from the endoplasmic reticulum (ER) suppresses translational initiation and inhibits post-translational processing and secretion of glycoproteins. This study explores the mechanism whereby ionomycin, a Ca2+ ionophore, and thapsigargin, an ER Ca(2+)-ATPase inhibitor, promote retention of alpha 1-antitrypsin (alpha 1-AT) bearing high mannose, endoglycosidase H (Endo H)-sensitive oligosaccharide side chains within the ER of HepG2 cells. Arrest occurred at the removal of mannose residues such that intermediates with Man7-9GlcNAc2 side chains accumulated with the Man8-9GlcNAc2 structures predominating. Maturation of alpha 1-AT bearing Man5-6GlcNAc2 side chains was unaffected. Inhibition of alpha 1-AT processing by ionomycin occurred independently of translational suppression. Forms of alpha 1-AT identical to those retained with ionomycin or thapsigargin were observed upon treatment with the alpha-1,2-mannosidase inhibitor 1-deoxymannojirimycin whereas castanospermine, an inhibitor of ER alpha-glucosidase I, produced different forms of the glycoprotein. Neither inhibitor impaired transport or secretion of alpha 1-AT. With brefeldin A, which causes redistribution of Golgi enzymes to the ER, alpha 1-AT was retained intracellularly but acquired resistance to Endo H. With ionomycin, thapsigargin, or 1-deoxymannojirimycin-treated cells, however, brefeldin A failed to promote further processing of the glycoprotein. Possible mechanisms for the suppression of alpha 1-AT processing at the alpha-1,2-mannosidase step by Ca(2+)-mobilizing agents are discussed. Excepting tunicamycin, traditional inhibitors of protein processing did not affect amino acid incorporation.
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PMID:Role of endoplasmic reticular calcium in oligosaccharide processing of alpha 1-antitrypsin. 838 May 85

Castanospermine is an indolizidine alkaloid that is found in the seeds of the Australian tree Castanospermum australe. These seeds have been reported to be toxic to animals and to cause severe gastrointestinal upset. In order to determine whether castanospermine is responsible for this toxicity, the alkaloid was injected into young mice or rats, and its effects on various intestinal disaccharidases were determined. Another indolizidine alkaloid, the alpha-mannosidase inhibitor swainsonine, was also tested to compare its effects to those of castanospermine. Castanospermine strongly and rapidly inhibited the activity of the disaccharidases, sucrase, maltase, and trehalase, with sucrase being the most sensitive to inhibition. The loss of activity of these enzymes, especially sucrase, in injected animals appeared to be due to a direct inhibition of enzyme activity, rather than to a change in the structure of the glycan chains of the enzyme, since only minor alterations in carbohydrates were observed. On the other hand, swainsonine, when injected into animals, also profoundly decreased the activity of the sucrase, but this alkaloid had no direct effect on sucrase activity although it did markedly alter the carbohydrate nature of this glycoprotein. This change in oligosaccharide structure may affect protein conformation, stability, or targeting, any or all of which may in turn affect activity. In in vitro studies with the purified enzyme, castanospermine was found to be a competitive inhibitor of intestinal sucrase, but it was a noncompetitive inhibitor of intestinal maltase. A number of other glucosidase inhibitors that inhibit sucrase activity in vitro are also described.
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PMID:The effects of castanospermine and swainsonine on the activity and synthesis of intestinal sucrase. 848 56

To examine the postnatal development of equine small intestine, biopsy specimens of jejunal mucosa from 8 ponies, between 6 and 28 weeks old, were subjected to analytical subcellular fractionation and assay of organelle marker enzymes. Fractionation revealed a reduction in the particulate brush border component of beta-galactosidase (lactase) activity between 6 and 28 weeks, and a corresponding increase in soluble activity, although the reduction in mean specific activity was not significant. There also was a decrease in the proportion of brush border to soluble aminopeptidase N activity, a relative loss of brush border gamma-glutamyltransferase activity, and a considerable decrease in the specific activity of alkaline phosphatase throughout the gradient fractions. In contrast, there were marked increases in activities of alpha-glucosidase (maltase) and sucrase in the older ponies, accompanied by considerable changes in the intracellular distribution of particulate alpha-glucosidase activity, which was predominantly associated with endoplasmic reticulum at 6 weeks, whereas the large increase in activity observed by 28 weeks was clearly associated with the brush border. The modal density of brush borders also increased with age, suggestive of an increase in the glycoprotein-to-lipid ratio of the microvillar membrane. In contrast to these brush border changes, there was relatively little alteration in the activities or density distributions of marker enzymes for endoplasmic reticulum, basolateral membranes, mitochondria, or lysosomes. These findings indicate that maturation of equine intestinal epithelium during the first few months of life results in major changes in the properties and enzyme composition of enterocyte brush borders.
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PMID:Subcellular biochemical changes during the development of the small intestine of pony foals. 853 83

N-glycosylation of the human immunodeficiency virus type-1 envelope (Env) glycoprotein precursor (gp160) occurs by transfer of Glc3Man9GlcNAc2 onto the nascent protein. Maturation then occurs via cleavage of the three Glc residues, which starts during translation. These events are considered necessary to create Env functional conformation: treatment with "alpha"-glucosidase inhibitors, but not alpha-mannosidase inhibitors (i) impairs gp160 cleavage into gp120 and gp41, (ii) diminishes the accessibility of gp120 V3 region, (iii) prevents gp120 binding to its CD4 receptor, and (iv) prevents gp41-mediated membrane fusion. These inhibitors are of therapeutic interest. Here, using a collection of parent and mutant CHO cells that possess mutations in different steps of glycosylation, we reassessed the role of glycans in both the processing and the properties of recombinant gp160 expressed from a vaccinia virus vector. Mutant cells were as follows: Lec23 (which lacks alpha-glucosidase I activity) produces a collection of triglucosylated structures (Glc3Man7-9GlcNAc2); LEC10 (which has increased GlcNAc transferase III activity) produces complex glycans with a bisected GlcNAc residue; Lec1 (which lacks GlcNAc transferase I) and Lec3.2.8.1 (which lacks GlcNAc transferase I and has decreased activity of CMP-NeuNAc and UDP-Gal translocases) produce Man5GlcNAc2 glycans at complex or hybrid sites. As expected, glycosylation of Env produced from mutants was affected but, irrespective of the glycosylation phenotype, (i) similar quantities of Env were synthesized, (ii) the immunoreactivity of V3 was similar, (iii) gp160 was efficiently cleaved into gp120 and gp41, (vi) Env was exposed at the cell membrane, (v) secreted gp120 bound CD4, and (vi) membrane gp41 was able to induce membrane fusion with CD4+ cells. Thus, the glycosylation alterations examined are dispensable for Env processing and biological activity in CHO cells. In particular, removal of the three outer Glc residues was not required per se for Env folding in this system because functional Env is obtained from Lec23 cells: it appears therefore that lack of modification is not equivalent to drug inhibition of modification. These data are discussed in the light of previous reports describing the use of glycosidase inhibitors to alter glycosylation.
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PMID:Biological properties of recombinant HIV envelope synthesized in CHO glycosylation-mutant cell lines. 861 25

Nectrisine, discovered as an immunomodulator, was found to inhibit alpha-glucosidase, alpha- and beta-mannosidases, beta-glucosidase and beta-N-acetylglucosaminidase, in that order of inhibition strength. Beta-Galactosidase, alpha-fucosidase, and neuraminidase were insensitive to this antibiotic. Also sensitive was the trimming glucosidase I which participates in the first step of modifying N-glycosidic oligosaccharide. Nectrisine demonstrated an inhibitory effect at the cellular level as strong as expected based on its action at enzyme levels; castanospermine and 1-deoxynojirimycin did not. Nectrisine and castanospermine suppressed syncytium formation and hemolytic activity in Newcastle disease virus (NDV)-infected BHK cells, without blocking the synthesis and cell-surface expression of HANA glycoprotein of NDV.
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PMID:Nectrisine is a potent inhibitor of alpha-glucosidases, demonstrating activities similarly at enzyme and cellular levels. 864 27

Perbutylated-N-butyl-1-deoxynojiromycin (p-N-butyl-DNJ, SC-49483), an alpha-glucosidase-1 inhibitor, is a candidate anti-HIV agent targeted against viral glycoprotein processing in host cell endoplasmic reticulum. The potential toxicity of this compound was evaluated in Sprague-Dawley rats after 4, 13, or 26 wk of oral administration at doses ranging from 300 to 3,670 mg/kg/day. In these studies, the target organs of p-N-butyl-DNJ effects were thyroid gland, salivary gland, stomach, and pancreas. The most prominent histologic change in these organs was the presence of clear or lightly eosinophilic vacuoles in the cytoplasm of thyroid follicular cells, gastric chief cells, salivary gland acinar cells, and exocrine pancreatic acinar cells. Ultrastructurally, these vacuoles were consistent with dilated rough endoplasmic reticulum, which sometimes contained homogeneously stained, moderately electron-dense material. The vacuoles in thyroid follicular cells contained pale eosinophilic colloidlike material consistent with accumulated thyroglobulin, as shown by immunohistochemical staining methods. The biological functions of these organs were not adversely affected as evidenced by the absence of clinical signs and the results of selected hormonal analyses. The morphologic changes were completely reversed after a 4-wk recovery period. The incidence and severity of histologic changes were decreased after 13 and 26 wk of treatment compared to 4 wk of treatment, indicating an attenuation of the host response or adaptation to the prolonged p-N-butyl-DNJ administration. We believe that morphologic changes in thyroid follicular cells, salivary gland acinar cells, pancreatic acinar cells, and gastric chief cells were the result of nonspecific inhibition of host alpha-glucosidase(s) by p-N-butyl-DNJ, causing clinically silent perturbation in host cell glycoprotein processing and/or glycoprotein transport.
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PMID:Pathology of perbutylated-N-butyl-1-deoxynojiromycin (an alpha-glucosidase-1 inhibitor) in Sprague-Dawley rats. 892 73

A number of unusual and rare carbohydrates were tested as potential inhibitors of various glycosidases, as well as inhibitors of N-linked oligosaccharide processing. The best inhibitors of several arylglycosidases and of glucosidase I were L-xylulose and L-fructose. Both of these sugars showed some inhibitory activity towards yeast alpha-glucosidase but were inactive against beta-glucosidase and other arylglycosidases. The inhibition of yeast alpha-glucosidase by L-xylulose was of a competitive nature and required a concentration of 1 x 10(-5) M for 50% inhibition. Both L-xylulose and L-fructose also inhibited the purified soybean glucosidase I, with 50% inhibition occurring at about 1 x 10(-4) M, but showed no inhibitory activity against soybean glucosidase II. When influenza virus-infected MDCK cells were raised in the presence of L-xylulose, there was a dose-dependent inhibition in the formation of complex types of oligosaccharides on the viral glycoproteins consistent with the inhibition of the processing glucosidase I. This inhibition resulted in the occurrence of oligosaccharides on the viral glycoproteins that were characterized as Glc3Man9(GlcNAc)2 structures. L-Fructose also inhibited glycoprotein processing in cell culture, and the inhibition resulted in the formation of similar oligosaccharides to those seen with L-xylulose. However, L-fructose was a poorer inhibitor than L-xylulose and required much higher concentrations for the same degree of inhibition. Neither of these compounds inhibited protein synthesis or the formation of lipid-linked saccharides in culture MDCK cells, even when tested at concentrations of 5 mg/ml (about 30 mM) of culture media.
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PMID:Inhibition of glycoprotein processing by L-fructose and L-xylulose. 902 40


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