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)

Midgut alpha-glucosidase (EC 3.2.1.20) activities were measured after ingestion of blood and sugar meals by the phlebotomine sandfly Phlebotomus langeroni. alpha-Glucosidase activity increased significantly within 1 hr after a blood meal and was maintained at significantly high activities until 48 hr postfeeding, when it fell to basal activity levels. Midgut alpha-glucosidase activity also increased within 1 hr of feeding on a sucrose meal, but there was no discernable peak in activity during the days postingestion. Differences in the induction of enzyme activity after a sugar meal compared to a blood meal might reflect the mode of ingestion of the two types of meal. The sugar meal is released intermittently into the midgut from the crop, in contrast to the bloodmeal, which is directed into the midgut immediately after ingestion and digested in a "batch" process. Nearly 90% of the alpha-glucosidase activity was associated with midgut cells of sugar fed sandflies compared to only 46% in blood fed insects. Isoelectrofocusing revealed the presence of seven alpha-glucosidases with isoelectric points between 4.3-5.8. No alpha-glucosidase activity was detected in the crop, indicating that glucosidases originate from the midgut epithelium rather than the salivary glands.
Comp Biochem Physiol B Biochem Mol Biol 1997 Jan
PMID:Carbohydrate digestion in sandflies: alpha-glucosidase activity in the midgut of Phlebotomus langeroni. 916 44

Twenty-six cyclic synthetic peptide combinatorial libraries (disulfides and lactams) of varying size and composition, representing 6.8 x 10(3) to 4.7 x 10(7) individual peptides, were synthesized along with their respective linear analogs. One of the hexapeptide lactam libraries (cyclo[xXxXxN]) was found to have significant alpha-glucosidase inhibitory activity. This library was carried through an iterative process of synthesis and screening, during which all of the five mixture positions (x and X) were successively defined. As the result of this process, potent and selective alpha-glucosidase inhibitors were identified.
Mol Divers 1996 Aug
PMID:Novel alpha-glucosidase inhibitors identified using multiple cyclic peptide combinatorial libraries. 923 14

The available amino acid sequences of the alpha-amylase family (glycosyl hydrolase family 13) were searched to identify their domain B, a distinct domain that protrudes from the regular catalytic (beta/alpha)8-barrel between the strand beta3 and the helix alpha3. The isolated domain B sequences were inspected visually and also analyzed by Hydrophobic Cluster Analysis (HCA) to find common features. Sequence analyses and inspection of the few available three-dimensional structures suggest that the secondary structure of domain B varies with the enzyme specificity. Domain B in these different forms, however, may still have evolved from a common ancestor. The largest number of different specificities was found in the group with structural similarity to domain B from Bacillus cereus oligo-1,6-glucosidase that contains an alpha-helix succeeded by a three-stranded antiparallel beta-sheet. These enzymes are alpha-glucosidase, cyclomaltodextrinase, dextran glucosidase, trehalose-6-phosphate hydrolase, neopullulanase, and a few alpha-amylases. Domain B of this type was observed also in some mammalian proteins involved in the transport of amino acids. These proteins show remarkable similarity with (beta/alpha)8-barrel elements throughout the entire sequence of enzymes from the oligo-1, 6-glucosidase group. The transport proteins, in turn, resemble the animal 4F2 heavy-chain cell surface antigens, for which the sequences either lack domain B or contain only parts thereof. The similarities are compiled to indicate a possible route of domain evolution in the alpha-amylase family.
J Mol Evol 1997 Sep
PMID:Domain evolution in the alpha-amylase family. 930 27

BT-R1, the Manduca sexta midgut receptor for the crystal toxin Cry1Ab produced by Bacillus thuringiensis ssp. berliner, was partly purified by gel filtration from M. sexta brush border membrane vesicles in the presence of the detergent CHAPS. Fractions containing BT-R1 were tested for their stability against degradation as indicated by retention of Cry1Ab binding on ligand blots. At 4 degrees C and pH 7.4 in the presence of Ca2+, BT-R1 was stable for up to 48 h but a 65% loss of binding was observed after 100 h. Under the same conditions, no loss of binding was observed in the presence of EGTA after 100 h. Cry1Ab binding decreased markedly as pH increased from 6 to 10 for incubations of 24 h at 4 degrees C. Increasing the temperature of incubation from 4 to 37 degrees C also decreased Cry1Ab binding. Neither metal ions nor free sulfhydryl groups are involved in Cry1Ab binding to BT-R1. A trypsin-like, metal-ion-dependent proteolytic activity co-eluted with BT-R1 during gel filtration. This endoproteolytic activity was unaltered by the addition of Cry1Ab. BT-R1 did not co-elute with peaks of aminopeptidase, alkaline phosphatase, alpha-glucosidase, beta-glucosidase and beta-galactosidase activities. When BT-R1 in the gel filtration fraction was further purified on a Mono Q anion exchange column, partial separation of the trypsin-like activity from BT-R1 was observed. BT-R1 could be removed from the appropriate Mono Q fraction by immunoprecipitation with only a slight decrease in this activity. These results demonstrate that there is no copurification of BT-R1 and these enzymes and that BT-R1 is unlikely to form complexes with them. Binding of Cry1Aa and Cry1Ac to BT-R1 in gel filtration fractions is similar to that of Cry1Ab, indicating that BT-R1 may be the high-affinity receptor for the Cry1A toxins. Binding of Cry1Ab to a 120 kDa protein has not been observed in this study.
Insect Biochem Mol Biol 1997 Jun
PMID:Further characterization of BT-R1, the cadherin-like receptor for Cry1Ab toxin in tobacco hornworm (Manduca sexta) midguts. 930 95

A microplate assay, for use with a variety of glycohydrolase enzymes, was developed to aid the screening of Chinese medicinal herb extracts for the presence of potential anti-viral and anti-lymphoma compounds. The microplate assay method described offers greater convenience, speed and reproducibility over existing methods. The enzymes tested were alpha-glucosidase, beta-glucosidase and beta-glucuronidase. The assay can be easily adapted for use with other glycohydrolase enzymes. Of the 12 herb extracts examined four did not inhibit any of the enzymes (< 50% inhibition), one inhibited alpha-glucosidase only (> 50% inhibition), six inhibited beta-glucuronidase only, and one inhibited both alpha-glucosidase and beta-glucuronidase. None of the extracts were capable of inhibiting beta-glucosidase to any significant extent.
Biochem Mol Biol Int 1997 Sep
PMID:Inhibition of glycohydrolase enzymes by aqueous extracts of Chinese medicinal herbs in a microplate format. 930 34

We analyzed a 5,770-bp genomic region of Drosophila virilis that contains a cluster of two maltase genes showing sequence similarity with genes in a cluster of three maltase genes previously identified in Drosophila melanogaster. The D. virilis maltase genes are designated Mav1 and Mav2. In addition to being different in gene number, the cluster of genes in D. virilis differs dramatically in intron-exon structure from the maltase genes in D. melanogaster, the transcriptional orientation of the genes in the cluster also differs between the species. Our findings support a model in which the maltase gene cluster in D. virilis and D. melanogaster evolved independently. Furthermore, while in D. melanogaster the maltase gene cluster lies only 10 kb distant from the larval cuticle gene cluster, the maltase and larval cuticle gene clusters in D. virilis are located very far apart and on a different chromosome than that expected from the known chromosome arm homologies between D. virilis and D. melanogaster. A region of the genome containing the maltase and larval cuticle gene clusters appears to have been relocated between nonhomologous chromosomes.
Mol Biol Evol 1997 Oct
PMID:The evolution of small gene clusters: evidence for an independent origin of the maltase gene cluster in Drosophila virilis and Drosophila melanogaster. 933 39

Experimentally induced diabetes in the rat resulted in an increased level of alpha-glycosidases in the intestine but a depression in their levels in the kidney. Rat intestine exhibited a differential stimulation of maltase, sucrase and trehalase activities. The variations depended on the duration of diabetes and the beta-cytotoxic compounds used i.e. alloxan and streptozotocin. The maximum elevation in terms of total units and specific activity was observed on the 30th day in the following order: maltase>sucrase>trehalase. A significant observation emerging from this study is that the level of intestinal enzymes increases while that of the kidney enzymes declined during the period. Although intestinal and renal alpha-glycosidases are known to be structurally and biochemically similar, their opposing responses to diabetes indicates that they are under different regulatory mechanisms in these tissues.
Biochem Mol Biol Int 1998 Apr
PMID:Responses of intestinal and renal alpha-glycosidases to alloxan and streptozotocin-induced diabetes: a comparative study. 958 78

Intestinal transport and metabolism of p-nitrophenyl alpha-disaccharides were studied. In the absorption of p-nitrophenyl alpha-melibioside, no compounds other than p-nitrophenyl alpha-melibioside were detected on either the mucosal or the serosal side. In the absorption of p-nitrophenyl alpha-maltoside, on the other hand, p-nitrophenyl alpha-glucoside was formed on the mucosal side to appear on the serosal side. p-Nitrophenol and p-nitrophenyl beta-glucuronide also appeared on the serosal side in the absorption of p-nitrophenyl alpha-maltoside, and the total amount transported to the serosal side was significantly decreased in the absence of Na+ (a cosubstrate of Na+/glucose cotransporter (SGLT1)). Furthermore, the total transport clearance of p-nitrophenyl alpha-glucoside formed from p-nitrophenyl alpha-maltoside on the mucosal side in the p-nitrophenyl alpha-maltoside absorption, was similar to that of the absorption of p-nitrophenyl alpha-glucoside itself. These results led to the conclusion that the intestinal absorption of disaccharide conjugate depended on disaccharidase, and the absorption of the alpha-maltose conjugate occurred sequentially by the maltase-catalyzed hydrolysis of the disaccharide conjugate and SGLT1-mediated transport of the glucose conjugate.
Res Commun Mol Pathol Pharmacol 1998 Apr
PMID:Intestinal metabolism and transport of alpha-disaccharide conjugates: the role of disaccharidase in the Na+/glucose cotransporter-mediated transport. 964 18

A major secretory protein of the human epididymis that is taken up by maturing spermatozoa is homologous to the leukocyte antigen CD52. The epididymis was shown to be the sole source of CD52 in seminal fluid, since CD52 could be detected in seminal plasma from sperm-containing ejaculates and not in ejaculates of vasectomized patients by Western blot analysis. The glycoprotein is not expressed in the testes. A fluorescence immunobinding assay was developed to quantify the amount of epididymal secretion of CD52 in the seminal plasma of various groups of fertile and infertile patients. Donor spermatozoa bearing CD52 were used as binding site tracers for free anti-CD52 antibody remaining after it had adsorbed CD52 from the seminal plasma to be assayed. The level of subsequent antibody binding to spermatozoa was measured by flow cytometry and the extent of binding inhibition was compared to a reference pool of seminal plasma to provide relative amounts of CD52 in test seminal plasma. There were no correlations between seminal plasma CD52 concentration and any semen parameter tested, including sperm concentration, percentage motility, normal sperm morphology or the concentration of seminal neutral alpha-glucosidase, fructose and zinc. There was a slight tendency towards an inverse relationship with the amount of CD52 on spermatozoa, but this was not significant. No differences were found among groups of patients classified by their semen parameters or fertility status. These findings indicate that the epididymal specific supply of CD52 is not a limiting factor for CD52 uptake onto spermatozoa.
Mol Hum Reprod 1998 May
PMID:Epididymal secretion of CD52 as measured in human seminal plasma by a fluorescence immunoassay. 966 31

An alpha-glucosidase cDNA clone derived from barley aleurone tissue was expressed in Pichia pastoris and Escherichia coli. The gene was fused with the N-terminal region of the Saccharomyces cerevisiae alpha-factor secretory peptide and placed under control of the Pichia AOX1 promoter in the vector pPIC9. Enzymatically active, recombinant alpha-glucosidase was synthesized and secreted from the yeast upon induction with methanol. The enzyme hydrolyzed maltose > trehalose > nigerose > isomaltose. Maltase activity occurred over the pH range 3.5-6.3 with an optimum at pH 4.3, classifying the enzyme as an acid alpha-glucosidase. The enzyme had a Km of 1.88 mM and Vmax of 0.054 micromol/min on maltose. The recombinant alpha-glucosidase expressed in E. coli was used to generate polyclonal antibodies. The antibodies detected 101 and 95 kDa forms of barley alpha-glucosidase early in seed germination. Their levels declined sharply later in germination, as an 81 kDa alpha-glucosidase became prominent. Synthesis of these proteins also occurred in isolated aleurones after treatment with gibberellin, and this was accompanied by a 14-fold increase in alpha-glucosidase enzyme activity.
Plant Mol Biol 1998 Oct
PMID:Expression of enzymatically active, recombinant barley alpha-glucosidase in yeast and immunological detection of alpha-glucosidase from seed tissue. 974 46


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