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)

Explants of pig small intestine were maintained at 37 degrees C in organ culture for periods up to 24 h in a system using Trowell T-8 medium supplemented with 10% foetal-calf serum. The mucosal morphology was well preserved during culture, as judged by light and electron microscopy. The explant contents of protein and two brush-border enzymes, microvillus aminopeptidase (EC 3.4.11.2) and dipeptidyl peptidase IV (EC 3.4.14.5), were not significantly modified during culture compared with controls, but a moderate, continuous release of both protein and enzyme activities into the medium was observed. Continuous labelling with [35S]methionine resulted in an even incorporation of radioactivity in the protein components, and the rate of labelling only moderately decreased over the 24 h period. The polypeptide compositions of sucrase (EC 3.2.1.48)--isomaltase (EC 3.2.1.10), maltase--glucoamylase (EC 3.2.1.20) lactase (EC 3.2.1.23)--phlorizin hydrolase (EC 3.2.1.62), microvillus aminopeptidase and aspartate aminopeptidase (EC 3.4.11.7) synthesized during culture were studied, and some were found to be similar to those of the pro-forms of the enzymes isolated from animals that had had their pancreatic duct disconnected 3 days before being killed. These results confirmed earlier findings of the existence of pro-forms of some of the microvillar enzymes and thus indicate a low activity of pancreatic proteinases in the culture system.
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PMID:Biosynthesis of intestinal microvillar proteins. Characterization of intestinal explants in organ culture and evidence for the existence of pro-forms of the microvillar enzymes. 709 36

Human hepatitis B virus (HBV) envelopes contain three distinct glycoproteins called L, M, and S HBsAg. Each is posttranslationally modified to contain N-linked oligosaccharides. N-linked oligosaccharides, after attachment to a polypeptide backbone, are processed by enzymes within the endoplasmic reticulum (ER). There is uncertainty about what role, if any, these N glycans and their modification in the ER play in the function of the HBV envelope proteins. By treating hepatoblastoma cultures which secrete HBV (HepG 2.2.15 cells) with inhibitors of different steps of the glycosylation and glycan modifying pathway, we provide evidence that glycosylation and the first step in the processing pathway are necessary for virion, but not subviral particle, secretion. That is, using a highly sensitive immunoprecipitation/polymerase chain reaction system, enveloped HBV could not be detected in the medium of HepG2.2.15 cells incubated with tunicamycin. However, HBV subviral particle secretion was not prevented by tunicamycin. Moreover, inhibitors of alpha-glucosidase I (the first step in the glycan processing pathway) also prevented virion secretion. Inhibitors of mannose trimming (a later step) and glycolipid synthesis, did not prevent virion secretion, defining the limits of the glycosylation requirements in secretion. These results demonstrate a requirement for N-glycosylation and glucosidase processing in the secretion of virions and further distinguish between the requirements for virion and subviral particle secretion.
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PMID:Evidence that N-linked glycosylation is necessary for hepatitis B virus secretion. 749 90

The proteolytic processing and secretion of a lysosomal enzyme, acid alpha-glucosidase, was studied by pulse-chase labeling with [35S]methionine in Tetrahymena thermophila CU-399 cells treated with ammonium chloride. This cell secreted a large amount of acid alpha-glucosidase into the cultured medium during starvation. The secretion was found to be repressed by addition of ammonium chloride (NH4Cl). Acid alpha-glucosidase was produced as a precursor form (108 kDa) and then processed to a mature polypeptide (105 kDa) within 60 min. This mature enzyme was secreted into the media within 2-3 h after chase, whereas the precursor form was not secreted by either control cells or NH4Cl-treated cells. NH4Cl did not affect the processing of the precursor acid alpha-glucosidase. Processing profile of this enzyme was apparently indistinguishable from that of the mutant MS-1 defective in lysosomal enzyme secretion. Furthermore, the purified extracellular (CU-399) and intracellular (MS-1) acid alpha-glucosidases were the same in molecular mass (105 kDa) and enzymatic properties. They contained no mannose 6-phosphate residues in N-linked oligosaccharides. These results suggested that unlike mammalian cells, Tetrahymena acid alpha-glucosidase may be transferred to lysosomes by a mannose 6-phosphate receptor-independent mechanism, and also that low pH was not essential for the proteolytic processing of precursor polypeptide.
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PMID:Processing and secretion of lysosomal acid alpha-glucosidase in Tetrahymena wild type and secretion-deficient mutant cells. 833 29

A putative alpha-glucosidase clone has been isolated from a cDNA library constructed from mRNA of barley aleurones treated with gibberellin A 3 (GA). The clone is 2752 bp in length and has an uninterrupted open reading frame encoding a polypeptide of 877 amino acids. A 680 amino acid region is 43% identical to human lysosomal alpha-glucosidase and other glycosyl hydrolases. In isolated aleurones, the levels of the corresponding mRNA increase strongly after the application of GA, similar to the pattern exhibited by low-pI alpha-amylase mRNA. High levels are also observed in the aleurone and scutellum after germination, while low levels are found in developing seeds. The genome contains a single form of this alpha-glucosidase gene and two additional sequences that may be related genes or pseudogenes.
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PMID:Molecular cloning and characterization of a gibberellin-inducible, putative alpha-glucosidase gene from barley. 861 48

The aim of this study was to determine the effects of a model of intestinal extrinsic denervation on mucosal structure and function. Six dogs underwent in situ neural isolation of the jejunoileum (Group 2); six other dogs served as operated controls (Group 1), and five nonoperated dogs were naive controls (Group 3). Thirty-centimeter segments of proximal jejunum and distal ileum were excised before (time zero) and at 2 weeks and 8 weeks postoperatively in Groups 1 and 2, while similar regions were removed at time zero in Group 3. Tissues were analyzed for morphology with quantitative morphometry, mucosal disaccharidase activities (sucrase, maltase, and lactase), and tissue content of selected regulatory peptides in transmural, mucosa/submucosa, and muscularis regions. In situ neural isolation had no significant or consistent effects on morphology/morphometry or on mucosal disaccharidase activities. Tissue content of neuropeptide Y decreased markedly (P < 0.002) in all layers of the jejunal and ileal walls, but tissue content of vasoactive inhibitory polypeptide, substance P, cholecystokinin, neurotensin, met-enkephalin, neurokinin A, somatostatin, and calcitonin gene-related peptide demonstrated only minor changes. The physiologic effects of intestinal transplantation (extrinsic denervation and disruption of intrinsic, enteric neural continuity, and lymphatic drainage) have little effect on morphology, mucosal disaccharidase activity, and tissue content of most regulatory peptides. How these minor alterations might affect enteric function, however, needs to be investigated.
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PMID:Neural isolation of the jejunoileum. Effect on tissue morphometry, mucosal disaccharidase activity, and tissue peptide content. 865 18

A cDNA encoding Mucor javanicus alpha-glucosidase was cloned and sequenced by the reverse transcription-polymerase chain reaction and rapid amplification of cDNA ends methods. The cDNA comprised 2,751 bp, and included an open reading frame which encodes a polypeptide of 864 amino acid residues with a molecular mass of 98,759 Da. The deduced amino acid sequence showed homology of fungal and mammalian alpha-glucosidases and related enzymes, and the sequence around the putative active site was well conserved among these enzymes. The cloned gene was expressed in Escherichia coli cells to produce the alpha-glucosidase, which hydrolyzes not only maltose, but also soluble starch.
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PMID:Molecular cloning, sequencing, and expression of a cDNA encoding alpha-glucosidase from Mucor javanicus. 883 45

The groEL gene of the alkaliphilic Bacillus sp. strain C-125 was cloned in Escherichia coli and sequenced. The groEL gene encoded a polypeptide of 544 amino acids and was preceded by the incomplete groES gene, lacking its 5'-end. The sequence of the derived amino acids was 87.5% identical to that of B. subtilis, 85.4% identical to that of B. stearothemophilus, and 60.9% identical to that of E. coli. The GroEL protein was expressed in E. coli. Purified GroEL protected yeast alpha-glucosidase from irreversible aggregation at a high temperature and the addition of Mg-ATP was essential for reactivation of the alpha-glucosidase. The addition of E. coli GroES increased recovery of the enzyme activity, indicating that C-125 GroEL could function in coordination with E. coli GroES.
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PMID:Molecular cloning and nucleotide sequence of the groEL gene from the alkaliphilic Bacillus sp. strain C-125 and reactivation of thermally inactivated alpha-glucosidase by recombinant GroEL. 898 60

A point mutation in the cDNA of human intestinal sucrase-isomaltase has been recently identified in phenotype II of congenital sucrase-isomaltase deficiency. The mutation results in a substitution of glutamine by proline at position 1098 (Q1098P) in the sucrase subunit. Expression of this mutant sucrase-isomaltase cDNA in COS-1 cells results in an accumulation of sucrase-isomaltase in the ER, intermediate compartment and the cis-Golgi cisternae similar to the accumulation in phenotype II intestinal cells. An interesting feature of the Q1098P substitution is its location in a region of the sucrase subunit that shares striking similarities with the isomaltase subunit and other functionally related enzymes, such as human lysosomal acid alpha-glucosidase and Schwanniomyces occidentalis glucoamylase. We speculated that the Q-->P substitution in these highly conserved regions may result in a comparable accumulation. Here we examined this hypothesis using lysosomal alpha-glucosidase as a reporter gene. Mutagenesis of the glutamine residue at position 244 in the homologous region of alpha-glucosidase to proline results in a protein that is neither transported to the lysosomes nor secreted extracellularly but accumulates in the ER, intermediate compartment and cis-Golgi as a mannose-rich polypeptide similar to mutant sucrase-isomaltase in phenotype II. We propose that the Q1098P and Q244P mutations (in sucrase-isomaltase and alpha-glucosidase, respectively) generate structural alterations that are recognized by a control mechanism, operating beyond the ER in the intermediate compartment or cis-Golgi.
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PMID:A mutation in a highly conserved region in brush-border sucrase-isomaltase and lysosomal alpha-glucosidase results in Golgi retention. 909 38

A cDNA encoding spinach alpha-glucosidase was cloned and sequenced by the reverse-transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) methods. The cDNA comprised 2867 bp, and included an open reading frame which encodes a polypeptide of 903 amino acid residues. The calculated molecular mass of 101 kDa was larger than those of native alpha-glucosidases in spinach seeds, which are 78, 78, 82, and 82 kDa by SDS-PAGE for alpha-glucosidase I, II, III, and IV, respectively. The deduced amino acid sequence included those of tryptic peptides from native enzymes. Southern blot analysis suggested that the alpha-glucosidase gene was a single-copy gene. These results indicate the possibility that the multiplicity of alpha-glucosidase in spinach occurs via post-translational modification.
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PMID:Molecular cloning and characterization of a cDNA encoding alpha-glucosidase from spinach. 913 69

A cDNA encoding sugar beet alpha-glucosidase was cloned from a library constructed from mRNA of suspension-cultured cells. The cDNA, 3056 bp in length, had an open reading frame encoding a polypeptide of 913 amino acid residues with a molecular mass of 102,078 Da, included only one of four regions which were conserved in the alpha-amylase family of enzymes. The deduced amino acid sequence from the analysis of the cDNA contained the sequences of the proteolysis peptides and the active site region peptide of sugar beet alpha-glucosidase. The primary structure indicated relatively high homology in the range of 28.2 to 54.3% to those for other alpha-glucosidases. The highest homology was found in barley alpha-glucosidase.
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PMID:Cloning and sequencing of a cDNA encoding alpha-glucosidase from sugar beet. 917 65


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