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)

alpha-Glucosidase was extracted from a homogenate of human kidney, initially with 0.02 M Tris-HCl buffer, pH 7.6, and subsequently with a mixture of 0.5% cholate and 0.5% Triton X-100 in the same buffer, pH 7.6. The enzyme in each of these two fractions was purified to the electrophoretically pure state by fractional precipitation with ammonium sulfate, column chromatographies on DEAE-cellulose, hydroxyapatite, Bio Gel A-1.5 m and affinity chromatography on heated glutinous rice. The two purified alpha-glucosidase preparations obtained were the same in enzymatic and proteochemical properties, and the molecular weight and isoelectric point estimated were 3 x 10(5) and 4.2, respectively. No evidence for subunit structure was obtained. The optimum pH for activity was 5.6 and the activity was drastically inhibited by Nojirimycin. The alpha-glucosidase readily hydrolyzed maltose, starch, and glycogen, producing only glucose. It hydrolyzed maltotriitol to split the non-reducing end glucose, but scarcely hydrolyzed maltitol or various other heteroglucosides examined. All these proteochemical and enzymatic properties of kidney alpha-glucosidase were the same as those of urine F-1 alpha-glucosidase. Also, kidney tissue alpha-glucosidase produced a clear precipitin line with antisera against urine F-1 alpha-glucosidase. These facts suggest that F-1 alpha-glucosidase in urine originates from kidney tissue.
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PMID:Identity of alpha-glucosidase of human kidney with urine F-1 alpha-glucosidase. 680 53

Glucosidase activities capable of removing the three glucose residues from Glc3Man9GlcNAc2 oligosaccharide were detected in a cell-free preparation of Saccharomyces cerevisiae X-2180. The glucosidase which cleaves the glucose residue at the nonreducing terminus (Glc3Man9GlcNAc2 oligosaccharide glucosidase) was equally distributed between the particulate and the supernatant fractions obtained after centrifugation of the yeast homogenate at 27,000 X g for 30 min. The membrane-bound activity was stimulated by Triton X-100, whereas the supernatant activity was not affected. The soluble Glc3Man9GlcNAc2 oligosaccharide glucosidase was partially purified from the supernatant by ammonium sulfate fractionation followed by DEAE-Sephadex chromatography. It was clearly separated from alpha-glucosidase, which acts onp-nitrophenyl-alpha-D-glucopyranoside, but still contained beta-glucosidase and alpha-mannosidase acting on p-nitrophenyl-beta-D-glucopyranoside and alpha-D-mannopyranoside, respectively. The Glc3Man9GlcNAc2 oligosaccharide glucosidase had a pH optimum of 6.8, and showed no requirement for divalent cations. The enzyme was very active with glucose-labeled Glc3Man9GlcNAc2, was slightly active with Glc2Man9GlcNAc2, and showed no activity with Glc1Man9GlcNAc2. These properties suggest that this enzyme is involved in the first step of processing of oligosaccharides after transfer from dolichyl pyrophosphate to proteins.
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PMID:Partial purification from Saccharomyces cerevisiae of a soluble glucosidase which removes the terminal glucose from the oligosaccharide Glc3Man9GlcNAc2. 701 69

Ammonia is a natural lysosomotropic compound. Concentrations of ammonium acetate > 2 mM impaired the phagocytic activity of BV-2 cells, an immortalized microglial cell line, as was determined by the uptake of fluorescent latex microspheres of different sizes. In contrast, an increase in the uptake of fluorescent dextran was observed with the elevation in ammonium acetate concentrations. This indicates that ammonia affects phagocytotic and pinocytotic activities of BV-2 cells differently. Interferon-gamma- and polyinosinic-polycytidylic acid-stimulated secretion of IL1 alpha as well as LPS-stimulated secretion of IL6 decreased with an elevation in ammonium acetate concentrations. The constitutive secretion of IL1 alpha was not significantly affected by ammonium acetate. However, an increase in LPS-stimulated IL1 alpha secretion was observed at 10 mM and 20 mM ammonium acetate. High concentrations of ammonia affected the activity of lysosomal enzymes of the BV-2 cells. Acid phosphatase and alpha-glucosidase activities increased with the increase in ammonium acetate up to 20 mM. The activity of cathepsin D was increased at 5 mM, but decreased at higher ammonia concentrations. The effects of ammonia on microglial functions are discussed with respect to pathogenetic mechanisms of dementia of the Alzheimer type.
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PMID:Effect of ammonia on endocytosis, cytokine production and lysosomal enzyme activity of a microglial cell line. 782 5

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. niger produced alpha-glucosidase, alpha-amylase and two forms of glucoamylase when grown in a liquid medium containing raw tapioca starch as the carbon source. The glucoamylases, which formed the dominant components of amylolytic activity manifested by the organism, were purified to homogeneity by ammonium sulfate precipitation, ion-exchange and two cycles of gel filtration chromatography. The purified enzymes, designated GA1 and GA2, a raw starch digesting glucoamylase, were found to have molar masses of 74 and 96 kDa and isoelectric points of 3.8 and 3.95, respectively. The enzymes were found to have pH optimum of 4.2 and 4.5 for GA1 and GA2, respectively, and were both stable in a pH range of 3.5-9.0. Both enzymes were thermophilic in nature with temperature optimum of 60 and 65 degrees C, respectively, and were stable for 1 h at temperatures of up to 60 degrees C. The kinetic parameters Km and V showed that with both enzymes the branched substrates, starch and amylopectin, were more efficiently hydrolyzed compared to amylose. GA2, the more active of the two glucoamylases produced, was approximately six to thirteen times more active towards raw starches compared to GA1.
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PMID:Purification and properties of two forms of glucoamylase from Aspergillus niger. 913 12

The archaeon Methanopyrus kandleri is the most thermophilic methanogen presently known. It contains a chaperonin (thermosome) which represents a 951 kDa homo-hexadecameric protein complex with NH4+-dependent ATPase activity. Since its synthesis is not increased upon heat shock, we set out to test its chaperone function. In order to obtain the chaperonin in amounts sufficient for functional investigations, the gene encoding the 60 kDa subunit was expressed in E. coili BL21 (DE3) cells. Purification yielded soluble, high-molecular-mass double-ring complexes, indistinguishable from the natural thermosome. In order to study the functional properties of the recombinant protein complex, pig citrate synthase, yeast alcohol dehydrogenase, yeast alpha-glucosidase, bovine insulin, and Thermotoga phosphoglycerate kinase were used as model substrates. The results demonstrate that the recombinant M. kandleri thermosome possesses a chaperone-like activity in vitro, inhibiting aggregation as the major off-pathway-reaction during thermal unfolding and refolding of proteins after chemical denaturation. However, the chaperonin only forms dead-end complexes with its non-native substrates, no release is detectable at temperatures between 25 and 60 degrees C.
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PMID:The recombinant thermosome from the hyperthermophilic archaeon Methanopyrus kandleri: in vitro analysis of its chaperone activity. 1006 37

A novel alpha-glucosidase with an apparent subunit mass of 59 +/- 0. 5 kDa was purified from protein extracts of Rhizobium sp. strain USDA 4280, a nodulating strain of black locust (Robinia pseudoacacia L), and characterized. After purification to homogeneity (475-fold; yield, 18%) by ammonium sulfate precipitation, cation-exchange chromatography, hydrophobic chromatography, dye chromatography, and gel filtration, this enzyme had a pI of 4.75 +/- 0.05. The enzyme activity was optimal at pH 6.0 to 6.5 and 35 degrees C. The activity increased in the presence of NH4+ and K+ ions but was inhibited by Cu2+, Ag+, Hg+, and Fe2+ ions and by various phenyl, phenol, and flavonoid derivatives. Native enzyme activity was revealed by native gel electrophoresis and isoelectrofocusing-polyacrylamide gel electrophoresis with fluorescence detection in which 4-methylumbelliferyl alpha-glucoside was the fluorogenic substrate. The enzyme was more active with alpha-glucosides substituted with aromatic aglycones than with oligosaccharides. This alpha-glucosidase exhibited Michaelis-Menten kinetics with 4-methylumbelliferyl alpha-D-glucopyranoside (Km, 0.141 microM; Vmax, 6.79 micromol min-1 mg-1) and with p-nitrophenyl alpha-D-glucopyranoside (Km, 0.037 microM; Vmax, 2.92 micromol min-1 mg-1). Maltose, trehalose, and sucrose were also hydrolyzed by this enzyme.
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PMID:Purification and characterization of an alpha-glucosidase from Rhizobium sp. (Robinia pseudoacacia L.) strain USDA 4280. 1038 82

High-isoelectric-point (pI) alpha-glucosidase was purified 7, 300-fold from an extract of barley (Hordeum vulgare) malt by ammonium sulfate fractionation, ion-exchange, and butyl-Sepharose chromatography. The enzyme had high activity toward maltose (k(cat) = 25 s(-1)), with an optimum at pH 4.5, and catalyzed the hydrolysis by a retaining mechanism, as shown by nuclear magnetic resonance. Acarbose was a strong inhibitor (K(i) = 1.5 microM). Molecular recognition revealed that all OH-groups in the non-reducing ring and OH-3 in the reducing ring of maltose formed important hydrogen bonds to the enzyme in the transition state complex. Mass spectrometry of tryptic fragments assigned the 92-kD protein to a barley cDNA (GenBank accession no. U22450) that appears to encode an alpha-glucosidase. A corresponding sequence (HvAgl97; GenBank accession no. AF118226) was isolated from a genomic phage library using a cDNA fragment from a barley cDNA library. HvAgl97 encodes a putative 96.6-kD protein of 879 amino acids with 93.8% identity to the protein deduced from U22450. The sequence contains two active site motifs of glycoside hydrolase family 31. Three introns of 86 to 4,286 bp interrupt the coding region. The four exons vary from 218 to 1,529 bp. Gene expression analysis showed that transcription reached a maximum 48 h after the start of germination.
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PMID:Purification, enzymatic characterization, and nucleotide sequence of a high-isoelectric-point alpha-glucosidase from barley malt. 1080 44

We isolated spontaneous mutants from Saccharomyces cerevisiae (baker's yeast V1) that were resistant to 2-deoxy-D-glucose and had improved fermentative capacity on sweet doughs. Three mutants could grow at the same rate as the wild type in minimal SD medium (0.17% Difco yeast nitrogen base without amino acids and ammonium sulfate, 0.5% ammonium sulfate, 2% glucose) and had stable elevated levels of maltase and/or invertase under repression conditions but lower levels in maltose-supplemented media. Two of the mutants also had high levels of phosphatase active on 2-deoxy-D-glucose-6-phosphate. Dough fermentation (CO2 liberation) by two of the mutants was faster and/or produced higher final volumes than that by the wild type, both under laboratory and industrial conditions, when the doughs were supplemented with glucose or sucrose. However, the three mutants were slower when fermenting plain doughs. Fermented sweet bakery products obtained with these mutants were of better quality than those produced by the wild type, with regard to their texture and their organoleptic properties.
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PMID:Improved properties of baker's yeast mutants resistant to 2-deoxy-D-glucose. 1152 34

Glycogen debranching enzyme was partially purified from bovine brain using a substrate for measuring the amylo-1,6-glucosidase activity. Bovine cerebrum was homogenized, followed by cell-fractionation of the resulting homogenate. The enzyme activity was found mainly in the cytosolic fraction. The enzyme was purified 5,000-fold by ammonium sulfate precipitation, anion-exchange chromatography, gel-filtration, anion-exchange HPLC, and gel-permeation HPLC. The enzyme preparation had no alpha-glucosidase or alpha-amylase activities and degraded phosphorylase limit dextrin of glycogen with phosphorylase. The molecular weight of the enzyme was 190,000 and the optimal pH was 6.0. The brain enzyme differed from glycogen debranching enzyme of liver or muscle in its mode of action on dextrins with an alpha-1,6-glucosyl branch, indicating an amino acid sequence different from those of the latter two enzymes. It is likely that the enzyme is involved in the breakdown of brain glycogen in concert with phosphorylase as in the cases of liver and muscle, but that this proceeds in a somewhat different manner. The enzyme activity decreased in the presence of ATP, suggesting that the degradation of brain glycogen is controlled by the modification of the debranching enzyme activity as well as the phosphorylase.
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PMID:Glycogen debranching enzyme in bovine brain. 1153 24


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