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)

In this study we investigated whether brain-gut peptides are implicated in the activation of the hypophysial-adrenal axis (HAA) in suckling rats treated orally with spermine. The first group of rats received i.p. injections of bombesin, vasoactive intestinal polypeptide (VIP), somatostatin or neurotensin, starting on day 11 of life, and killed on day 14. The small intestine was removed and analysed for its content of proteins, DNA, polyamines and for its specific activity (SA) of disaccharidases. The second group of rats received one of the hormones cited above and was killed 45 min after the treatment for determination of corticosterone plasma concentration. Rats of the third group were adrenalectomised then treated with bombesin as the first group. The fourth group of rats was orally treated with spermine and sacrificed 2, 3, 4, 6 and 8 h thereafter for analysis of plasma and intestinal concentrations of bombesin. The i.p. injection of bombesin increased the sucrase and maltase SA in the whole small intestine, while it decreased the lactase SA in the distal part. Intestinal weight and length, contents of DNA, protein, spermidine and spermine, and corticosterone plasma levels were enhanced by bombesin treatment. Somatostatin, neurotensin and VIP were ineffective on all the parameters studied. Adrenalectomy, in bombesin-treated rats, decreased the sucrase and maltase SA in the whole intestine, and decreased the lactase SA in the proximal intestine. It has no effect on intestinal weight and length, and protein content. Oral administration of spermine had no effect on plasma concentration of bombesin, whereas it decreased the content of this peptide in the whole small intestine. It is possible that bombesin may control intestinal development in suckling rats and be a link between the ingestion of spermine and the liberation of corticosterone by the adrenal glands.
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PMID:Involvement of bombesin in spermine-induced corticosterone secretion and intestinal maturation in suckling rats. 920 97

The role of glucose trimming in the endoplasmic reticulum of Saccharomyces cerevisiae was investigated using glucosidase inhibitors and mutant strains devoid of glucosidases I and II. These glucosidases are responsible for removing glucose residues from the N-linked core oligosaccharides attached to newly synthesized polypeptide chains. In mammalian cells they participate together with calnexin, calreticulin and UDP-glucose:glycoprotein glucosyltransferase in the folding and quality control of newly synthesized glycoproteins. In S.cerevisiae, glucosidase II is encoded by the GLS2 gene, and glucosidase I, as suggested here, by the CWH41 gene. Using castanospermine (an alpha-glucosidase inhibitor) and yeast strains defective in glucosidase I, glucosidase II and BiP/Kar2p, it was demonstrated that cell wall synthesis depends on the two glucosidases and BiP/Kar2p. In double mutants with defects in both BiP/Kar2p and either of the glucosidases the phenotype was particularly clear: synthesis of 1,6-beta-glucan_a cell wall component_was reduced; the cell wall displayed abnormal morphology; the cells aggregated; and their growth was severely inhibited. No defects in protein folding or secretion could be detected. We concluded that glucose trimming in S.cerevisiae is necessary for proper cell wall synthesis, and that the glucosidases function synergistically with BiP/Kar2p in this process.
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PMID:Cell wall 1,6-beta-glucan synthesis in Saccharomyces cerevisiae depends on ER glucosidases I and II, and the molecular chaperone BiP/Kar2p. 943 Jun 31

Acid alpha-glucosidase (GAA) hydrolyzes alpha-1, 4 and alpha-1, 6 glucosidic linkages of oligosaccharides and degrades glycogen in the lysosomes. The full-length GAA I cDNA, pQAM8, was isolated from a cDNA library derived from Japanese quail liver. The cDNA is 3569 base pairs long and has an open reading frame capable of coding 932 amino acids. The deduced amino acid sequence shares 52% identity with human GAA. Transfection of expression vector pETAM8 into COS-7 cells or acid maltase deficient (AMD) quail embryonic fibroblasts increased the level of GAA 20-50-fold. Compared to normal quail, the levels of GAA I mRNA were significantly reduced in the muscle, liver, heart, and brain of AMD quails, suggesting the GAA deficiency in AMD quail is due to a lack of GAA I mRNA. A second GAA II cDNA was identified after probing the cDNA library from the ovarian large follicles of quails with a PCR product derived from cultured quail skin fibroblasts. This clone having 3.1 kb insert, has GAA activity as well (3 to 10 fold increase). This cDNA, designated GAA II, predicted an 873 amino acid polypeptide showing 63% identity to human GAA and 51% identity to the GAA I. The RT-PCR analysis demonstrated that GAA II mRNAs were barely detectable in normal tissues, while they were enhanced to higher levels in AMD tissues. These results suggest that GAA II expression is up-regulated at the transcription levels, and quail GAA gene redundancy performs the same function of satisfying GAA demand at the two different phases represented by normal and AMD.
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PMID:Molecular cloning of acid alpha-glucosidase cDNA of Japanese quail (Coturnix coturnix japonica) and the lack of its mRNA in acid maltase deficient quails. 954 Aug 58

Several proteins (avidin, carboxypeptidase B, glucose-6-phosphate dehydrogenase, glutamate dehydrogenase, maltase, and peroxidase) composed of one to six subunits were irradiated in the frozen state. Each irradiated protein was examined by size-exclusion chromatography (SEC) and by denaturing gel electrophoresis (SDS-PAGE). All these proteins eluted from SEC as a single peak even though SDS-PAGE showed cleavage of the polypeptide backbone of the monomers. Thus, fragmentation of the subunits did not result in dissociation of the oligomeric structure.
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PMID:Radiation effects on the native structure of proteins: fragmentation without dissociation. 958 17

Fusion proteins of monomeric alpha-glucosidase from Saccharomyces cerevisiae containing N- or C-terminal hexa-arginie peptides were expressed in the cytosol of Escherichia coli in soluble form. The polycationic peptide moieties allow noncovalent binding of the denatured fusion proteins to a polyanionic solid support. Upon removal of the denaturant, refolding of the matrix-bound protein can proceed without perturbation by aggregation. However, nonspecific interactions of the denatured polypeptide, or of folding intermediates, with the matrix cause a drastic decrease in renaturation under suboptimal folding conditions. At low salt concentrations, ionic interactions of the refolding polypeptide with the matrix result in lower yields of renaturation. At higher salt concentrations, renaturation is prevented by hydrophobic interactions with the matrix. Apart from ionic strength, renaturation of the denatured matrix-bound fusion protein must be optimized with respect to pH, temperature, cosolvents, and matrix material used. Under optimum conditions, immobilized alpha-glucosidase can be renatured with a high yield at protein concentrations up to 5 mg/ml, whereas folding of the wild-type enzyme in solution is feasible only at an extremely low protein concentration (15 micrograms/ml). Thus, folding of the immobilized alpha-glucosidase allows an extremely high yield of the renaturated model protein. The technology should be applicable to other proteins that tend to aggregate during refolding.
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PMID:Improved refolding of an immobilized fusion protein. 963 Aug 95

Using an Arabidopsis thaliana expressed sequence tag with sequence similarity to human lysosomal alpha-glucosidase as a probe, a potato cDNA was isolated. The cDNA encodes a polypeptide with an Mr value of 105,400 and the most significant matches of the deduced amino acid sequence are with members of family 31 of glucosyl transferase. The potato cDNA was expressed in a strain of Saccharomyces cerevisiae that is deficient in maltase activity and unable to grow using maltose as a carbon source (ABYSMAL81). Expression of the potato cDNA in the mutant yeast strain restores its ability to use maltose as a carbon source for growth. Additionally, alpha-glucosidase activity could be measured in extracts of the yeast cells following complementation. A range of maltodextrins were substrates for this activity. The steady-state expression level of the potato alpha-glucosidase gene was low in most tissues examined, the highest levels occurring in sprouting tubers and source leaves.
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PMID:cDNA cloning and characterisation of an alpha-glucosidase gene from potato (Solanum tuberosum L.). 968 Sep 91

The maltose degradation operon containing genes encoding maltose phosphorylase mapA and phosphoglucomutase pgmA from Lactobacillus sanfranciscensis DSM20451T were cloned and expressed in Escherichia coli. These genes represent the first genetic data available for this species beyond taxonomic classification. MapA encodes a 754-amino acid polypeptide representing maltose phosphorylase, MapA, with a calculated molecular mass of 85.7 kDa. Comparative sequence analysis showed that mapA is of a new type distinct from other alpha-glucosidase genes sequenced so far. Putatively, pyridoxal 5'-phosphate is required as cofactor. The deduced amino acid sequence of pgmA shows an overall similarity of 39% to the phosphoglucomutase of Lactococcus lactis. pgmA is separated by a single nucleotide from the preceding mapA gene indicating effective translation by translational coupling. Upon subcloning mapA was heterologously expressed in E. coli. Additionally, upstream of the maltose-degrading operon ORF1 and ORF2 are located in the opposite direction. These genes show homology to fabZ and accB from E. coli and Bacillus subtilis, respectively, both involved in fatty acids biosynthesis.
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PMID:Maltose metabolism of Lactobacillus sanfranciscensis: cloning and heterologous expression of the key enzymes, maltose phosphorylase and phosphoglucomutase. 985 Oct 37

Apoplastic alpha-glucosidases occur widely in plants but their function is unknown because appropriate substrates in the apoplast have not been identified. Arabidopsis contains at least three alpha-glucosidase genes; Aglu-1 and Aglu-3 are sequenced and Aglu-2 is known from six expressed sequence tags. Antibodies raised to a portion of Aglu-1 expressed in Escherichia coli recognize two proteins of 96 and 81 kD, respectively, in vegetative tissues of Arabidopsis, broccoli (Brassica oleracea L.), and mustard (Brassica napus L.). The acidic alpha-glucosidase activity from broccoli flower buds was purified using concanavalin A and ion-exchange chromatography. Two active fractions were resolved and both contained a 96-kD immunoreactive polypeptide. The N-terminal sequence from the 96-kD broccoli alpha-glucosidase indicated that it corresponds to the Arabidopsis Aglu-2 gene and that approximately 15 kD of the predicted N terminus was cleaved. The 81-kD protein was more abundant than the 96-kD protein, but it was not active with 4-methylumbelliferyl-alpha-D-glucopyranoside as the substrate and it did not bind to concanavalin A. In situ activity staining using 5-bromo-4-chloro-3-indolyl-alpha-D-glucopyranoside revealed that the acidic alpha-glucosidase activity is predominantly located in the outer cortex of broccoli stems and in vascular tissue, especially in leaf traces.
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PMID:Structure, properties, and tissue localization of apoplastic alpha-glucosidase in crucifers. 995 33

Glucosidase I is an important enzyme in N-linked glycoprotein processing, removing specifically distal alpha-1,2-linked glucose from the Glc3Man9GlcNAc2 precursor after its en bloc transfer from dolichyl diphosphate to a nascent polypeptide chain in the endoplasmic reticulum. We have identified a glucosidase I defect in a neonate with severe generalized hypotonia and dysmorphic features. The clinical course was progressive and was characterized by the occurrence of hepatomegaly, hypoventilation, feeding problems, seizures, and fatal outcome at age 74 d. The accumulation of the tetrasaccharide Glc(alpha1-2)Glc(alpha1-3)Glc(alpha1-3)Man in the patient's urine indicated a glycosylation disorder. Enzymological studies on liver tissue and cultured skin fibroblasts revealed a severe glucosidase I deficiency. The residual activity was <3% of that of controls. Glucosidase I activities in cultured skin fibroblasts from both parents were found to be 50% of those of controls. Tissues from the patient subjected to SDS-PAGE followed by immunoblotting revealed strongly decreased amounts of glucosidase I protein in the homogenate of the liver, and a less-severe decrease in cultured skin fibroblasts. Molecular studies showed that the patient was a compound heterozygote for two missense mutations in the glucosidase I gene: (1) one allele harbored a G-->C transition at nucleotide (nt) 1587, resulting in the substitution of Arg at position 486 by Thr (R486T), and (2) on the other allele a T-->C transition at nt 2085 resulted in the substitution of Phe at position 652 by Leu (F652L). The mother was heterozygous for the G-->C transition, whereas the father was heterozygous for the T-->C transition. These base changes were not seen in 100 control DNA samples. A causal relationship between the alpha-glucosidase I deficiency and the disease is postulated.
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PMID:A novel disorder caused by defective biosynthesis of N-linked oligosaccharides due to glucosidase I deficiency. 1078 35

cDNA encoding Schizosaccharomyces pombe alpha-glucosidase was cloned from a library constructed from mRNA of the fission yeast, and expressed in Saccharomyces cerevisiae. The cDNA, 4176 bp in length, included a single ORF composed of 2910 bp encoding a polypeptide of 969 amino-acid residues with M(r) 106 138. The deduced amino-acid sequence showed a high homology to those of alpha-glucosidases from molds, plants and mammals. Therefore, the enzyme was categorized into the alpha-glucosidase family II. By site-directed mutagenesis, Asp481, Glu484 and Asp647 residues were confirmed to be essential in the catalytic reaction. The carboxyl group (-COOH) of the Asp647 residue was for the first time shown to be the most likely proton donor acting as the acid catalyst in the alpha-glucosidase of family II. Studies with the chemical modifier conduritol B epoxide suggested that the carboxylate group (-COO-) of the Asp481 residue was the catalytic nucleophile, although the role of the Glu484 residue remains obscure.
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PMID:Carboxyl group of residue Asp647 as possible proton donor in catalytic reaction of alpha-glucosidase from Schizosaccharomyces pombe. 1129 44


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