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 effect of dietary thiamin deficiency has been studied on intestinal functions and chemical composition of brush border membranes in rats. Intestinal uptake of glucose, glycine, alanine, and leucine was significantly stimulated in thiamin deficiency compared to pair-fed control group. Studies with glucose and glycine revealed that stimulation of the absorption process occurs only in the presence of Na+ but not in its absence. Km measured in the presence of 140 mM Na+ for glucose and glycine uptakes was reduced by 56 and 41%, respectively, but Vmax remained unaltered in vitamin deficiency. There was no change in these parameters in Na+-free medium (Km = 31.3 and 23.3 mM; Vmax = 17.2 to 19.7 and 13.5 to 16.4 mumol/10 min/g wet tissue, respectively) under these conditions. The activities of brush border sucrase, lactase, maltase, alkaline phosphatase, and leucine aminopeptidase were reduced by 42 to 66% in thiamin deficiency, compared to pair-fed controls. Kinetic studies with sucrase and alkaline phosphatase evinced that a decrease in Vmax (61 and 64%, respectively) with no change in Km (33.8 and 4.3 mM, respectively) was responsible for observed impairment in the enzyme activities in thiamin deficiency. Microvillus membrane proteins expressed on dry membrane basis were reduced by 20% in thiamin-deficient intestine. There was no difference in membrane sialic acid, cholesterol, phospholipids, and triglycerides fractions under these conditions. It is suggested that thinning of the microvillus membrane may be implicated in observed aberrations of intestinal functions in thiamin-deprived animals.
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PMID:Effect of dietary thiamin deficiency on intestinal functions in rats. 646 54

The present study was performed to investigate the enzymatic changes in dystrophic chickens compared to those of dystrophic mice. The activities of 14 kinds of aminopeptidases, 5 kinds of endopeptidase, 4 kinds of glycosidases, phosphatase, esterase, and ribonuclease were measured in muscles of control and dystrophic chickens. When the enzyme activities were expressed as specific activity per unit weight of organs, only some of them were found to be significantly elevated in dystrophic chickens; e.g., alanine aminopeptidase (Ala-AP), Gly-AP and cathepsin D. On the contrary, the activities of alpha-D-glycosidase, alpha-D-galactosidase and alpha-D-mannosidase were significantly decreased. Muscular protein contents of dystrophic chickens also tended to be lower than those of controls. These observations offer a striking contrast with the one obtained in the study on dystrophic mice. However, when expressed as specific activity per mg protein, many enzyme activities were found to be significantly elevated suggesting an extensive abnormality of metabolism in dystrophic chickens. Among 14 kinds of aminopeptidase activities, highly significant elevations were seen especially in AP-A, AP-B, Gly-AP, Ala-AP, Ser-AP, Pro-AP, Leu-AP, Met-AP and Trp-AP. Interestingly enough, a statistical approach suggested a significant correlation between the aminopeptidase changes of dystrophic chickens with those of dystrophic mice. In addition to aminopeptidases, there were highly significant increases in the activities of cathepsin D, alpha-D-glucosidase, beta-D-galactosidase, alpha-D-mannosidase, esterase and RNase. These results indicate that the intramuscular metabolic abnormality of dystrophic chickens are generally different from but partly resembled with those of dystrophic mice.
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PMID:Intramuscular enzyme abnormalities of dystrophic chickens compared to those of dystrophic mice. 701 13

To characterize the amino acid transport system in basolateral membranes and to test for possible intracellular loci of amino acid transport activity, we surveyed the distribution of L-alanine transport activity in rabbit proximal tubular cells and LLC-PK1/Cl4 cells. A three-dimensional separation procedure based on differential sedimentation, density gradient centrifugation, and counter-current distribution resolved 21 physically and biochemically distinct membrane populations from rabbit cortex. Inhibition of L-alanine transport by phenylalanine and N-(methylamino)isobutyric acid was used to delineate parallel amino acid transport pathways. Population n was identified as brush border membranes by virtue of its 16-fold maltase enrichment; 94% of its Na(+)-dependent alanine transport activity was mediated by systems previously shown to be characteristic of brush border membranes. Two populations, c' and c", which accounted for 25% of the total Na,K-ATPase activity, were identified as basalateral membranes on the basis of Na,K-ATPase cumulative enrichment factors of 15 and 21; 82% of the total alanine transport in these populations was mediated by a Na(+)-independent system similar to the classical system L. Na,K-ATPase, Na(+)-independent and Na(+)-dependent alanine transport activities were associated with intracellular membrane populations as well as with the plasma membranes. The major intracellular locus of Na,K-ATPase activity, population i accounted for roughly 31% of the Na,K-ATPase, maximally enriched ninefold; it contained 29% of the total system L transport activity. Population l, which was identified as endoplasmic reticulum because it was the major locus of membrane-bound NADPH cytochrome c reductase activity, contained 44% of the total system A transport. Three distinct Golgi-derived populations, m', m", and o, accounted for 39% of the total system A transport. A survey of the amino acid transport systems in LLC-PK1/Cl4 cells showed that the majority of system A-mediated amino acid transport was present in membranes of intracellular and possibly apical origin. The presence of large intracellular pools of amino acid transport activities might reflect newly synthesized transport proteins, ongoing membrane recycling or, perhaps, intracellular reserves available for rapid recruitment to the plasma membrane.
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PMID:Complex subcellular distribution of sodium-dependent amino acid transport systems in kidney cortex and LLC-PK1/Cl4 cells. 812 99

Glucose intolerance and diabetes mellitus are both prevalent in patients with chronic liver diseases. We examined the efficacy and systemic safety of therapy with an alpha-glucosidase inhibitor, acarbose, in diabetes mellitus associated with chronic liver diseases. Twenty patients with chronic hepatitis or liver cirrhosis and overt diabetes mellitus received acarbose (taken orally) for 8 weeks. The initial dosage of acarbose was 50 mg three times daily, taken before meals; this was increased to 100 mg three times daily after 2 weeks. The mean fasting plasma glucose level was 173.7 +/- 18.6 mg/dl (mean +/- SE) at entry, and was significantly decreased to 132.9 +/- 7.5 mg/dl (P < 0.05) after 8 weeks of acarbose treatment. The improved glycemic control was reflected by a significant decrease in glycosylated hemoglobin (HbA1c) from 7.2 +/- 0.3% at entry to 6.3 +/- 0.2% (P < 0.05) after 8 weeks. Serum levels of both aspartate and alanine aminotransferases fluctuated during acarbose treatment, probably due to the natural course of chronic liver diseases, but the mean values had decreased after 8 weeks of treatment. Plasma ammonia levels increased, from 61.3 +/- 10.7 micrograms/dl to 71.1 +/- 9.6 micrograms/dl after 8 weeks of acarbose treatment but the increase was not significant. Clinically significant elevation of plasma ammonia concentration was seen in 2 cirrhotic patients (121 and 124 micrograms/dl); this was asymptomatic and gradually returned to the normal range despite continuous acarbose treatment in one patient, and was reversed after the withdrawal of acarbose with the concomitant administration of lactulose in the other patient. No other blood tests results, including albumin, cholinesterase, and prothrombin time, or lipid profile and nutritional status, in terms of rapid turnover proteins, prealbumin, retinol binding protein, and transferin, were altered throughout the study period. These results indicate that diabetes mellitus associated with chronic liver diseases may be safely and effectively treated with acarbose. However, clinicians must be aware of the possibility of hyperammonemia when they prescribe acarbose for patients with diabetes mellitus and advanced liver cirrhosis.
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PMID:Safe and effective treatment of diabetes mellitus associated with chronic liver diseases with an alpha-glucosidase inhibitor, acarbose. 943 16

A library of 72 compounds related to N- [4-(benzyloxy) benzoyl]alanine (I) was synthesized, prepared and screened for alpha-glucosidase inhibitory activity. Four compounds showed potent inhibition, six compounds moderate inhibition, and 16 were weak inhibitors. One compound, N- [4-(benzyloxy) benzoyl] serine, was found to be a potent inhibitor of alpha-glucosidase with 100% inhibition at 1 micro M. This inhibitor was at least five times more potent than the lead compound I.
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PMID:Identification of novel alpha-glucosidase inhibitors by screening libraries based on N- [4-(benzyloxy) benzoyl] alanine derivatives. 1247 Feb 67

Per os administration of Vilon (Lys-Glu) or Epithalon (Ala-Glu-Asp-Gly) to aged Wistar rats for 1 month significantly increased activity of membrane enzymes maltase and alkaline phosphatase in epithelial layer of the small intestine. In addition, Vilon significantly increased activity of cytosolic glycyl-L-leucine dipeptidase in the stromal and seromuscular layers of the small intestine in comparison with the control rats not treated with this agent. These findings suggest improvement of trophic and barrier functions of the small intestine and corroborate the hypothesis on the existence of not only epithelial, but also subepithelial enzymatic barrier supporting the enzyme system in the small intestine, especially in aged animals.
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PMID:Effect of vilon and epithalon on activity of enzymes in epithelial and subepithelial layers in small intestine of old rats. 1266 Aug 39

The MAL-activator genes of Saccharomyces cerevisiae encode regulatory proteins required for the expression of the structural genes encoding maltose permease and maltase. Residues within the C-terminal region of the Mal63 protein required for negative regulation were previously identified. Evidence suggested that the C-terminal domain is also involved in positive regulatory functions, such as inducer responsiveness and transactivation in the context of a full-length protein. Charged-cluster to alanine scanning mutagenesis of the regulatory domain of MAL63 and the constitutive MAL43-C were undertaken to identify distinct regions within Mal63p involved in positive functions and to define their roles in induction. Mutations that affect the ability to activate transcription in the inducible MAL63 but have no effect in the constitutive MAL43-C define regions that function in induction. Those that affect both the inducible and constitutive alleles define regions involved in activation more generally. Mutations in MAL63 fell into three classes, those that have little or no impact on activity, those that decrease activity, and those that enhance function. Mutations from these classes mapped to distinct regions of the protein, identifying a region of approximately 90 residues (residues 331-423) involved in maltose sensing and an approximately 50-residue region at the extreme C-terminus (residues 420-470) required for activation, such as the formation and/or maintenance of an active state. These studies support a model for MAL-activator function which involves complex protein-protein interactions and overlapping negative and positive regulatory regions.
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PMID:Clustered-charge to alanine scanning mutagenesis of the Mal63 MAL-activator C-terminal regulatory domain. 1450 2

Fluorogenic artificial substrates facilitate sensitive enzyme activity measurements for a variety of processes in soil and other environmental samples. It is possible to use in situ pH for measurements on condition that the substrates are chemically stable. We studied the stability of 12 different methyl umbellipherone (MUF) and amino methyl coumarine (AMC) derivatives used as substrates for arylsulphatase, alpha-glucosidase, beta-glucosidase, beta-xylosidase, cellobiosidase, chitinase, phosphomonoesterase (PME), phoshodiesterase (PDE), esterase, lipase and alanine- and leucine aminopeptidases (AP) over the pH range from 4.0 to 8.0 in modified universal buffer (MUB). Stability of the substrates for lipase (4-MUF-heptanoate) and esterase (4-MUF-acetate) measurements was poor, especially at the higher pH values. Chitinase substrate, 4-MUF-N-acetyl-beta-D-glucosamide, was unstable at high pH values whereas the substrate for PME activity measurement (4-MUF-phosphate) disintegrated at low pH. The other substrates and MUF and AMC standard solutions were stable over the pH range studied. The optima between pH 4 and 8 of the 11 different enzyme activities were measured in three forest and two agricultural soil samples and in one activated sludge sample. In soil, for alanine and leucine AP the pH optima were usually 7.5 or higher, for arylsulphatase, beta-glucosidase, beta-xylosidase, esterase and PDE between 4 and 5.5, and for cellobiosidase between 4 and 5. alpha-Glucosidase had an optimum below 5.5 but also exhibited high activity at pH 7. Soil-dependent variation in pH optima were observed for chitinase, esterase, PDE and PME. Enzyme activities were also measured in 0.5 M acetate buffer at pH 5.5. This buffer yielded the highest activities in all soil samples for arylsulphatase, PDE and PME.
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PMID:Stability of the fluorogenic enzyme substrates and pH optima of enzyme activities in different Finnish soils. 1559 94

Yeast alpha-glucosidase I (Cwh41p) encoded by CWH41 is an endoplasmic reticulum (ER) membrane-bound glycoprotein (833 residues), which plays an important role in the early steps of the N-glycosylation pathway. In this study functional expression of three truncated fragments of Cwh41p, all containing the catalytic region, was investigated. Cwht1p (E35-F833), with deletion of the N-terminus and transmembrane domain, was expressed as a catalytically active fragment while R320-F833(Cwht2p) and M526-F833 (Cwht3p) were not detected. Significantly higher glucosidase I activity was found in a soluble extract from yeast overexpressing CWHT1 (1,400 U/g biomass) than yeast overexpressing CWH41 (300 U/g biomass). Cwht1p was purified as a soluble 94 kDa non-glycosylated protein with a specific activity (3,600 U/mg protein) comparable to that of the soluble alpha-glucosidase I (3000 U/mg protein). These findings indicate that the active conformation of the enzyme is not dependent on protein glycosylation and suggest that the M1-I28 region of Cwh41p carries an ER-targeting signal sequence. In addition, two highly conserved carboxylic acid residues, E580 and D584 of Cwht1p (corresponding to E613 and D617 of Cwh41p), located within the catalytic domain of yeast enzyme were subjected to mutation. Substitution of each residue with Ala resulted in low expression and undetectable glucosidase I activity. These findings indicate that E613 and D617 play a crucial role in maintaining alpha-glucosidase I activity.
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PMID:Truncations and functional carboxylic acid residues of yeast processing alpha-glucosidase I. 1745 96

Bacillus stearothermophilus alpha-1,4-glucosidase (BS) is highly specific for alpha-1,4-glucosidic bonds of maltose, maltooligosaccharides and alpha-glucans. Bacillus thermoglucosdasius oligo-1,6-glucosidase (BT) can specifically hydrolyse alpha-1,6 bonds of isomaltose, isomaltooligosaccharides and alpha-limit dextrin. The two enzymes have high homology in primary structure and belong to glycoside hydrolase family 13, which contain four conservative regions (I, II, III and IV). The two enzymes are suggested to be very close in structure, even though there are strict differences in their substrate specificities. Molecular determinants of substrate recognition in these two enzymes were analysed by site-directed mutagenesis. Twenty BT-based mutants and three BS-based mutants were constructed and characterized. Double substitutions in BT of Val200 -->Ala in region II and Pro258 -->Asn in region III caused an appearance of maltase activity compared with BS, and a large reduction of isomaltase activity. The values of k(0)/K(m) (s(-1). mM(-1)) of the BT-mutant for maltose and isomaltose were 69.0 and 15.4, respectively. We conclude that the Val/Ala200 and Pro/Asn258 residues in the alpha-glucosidases may be largely responsible for substrate recognition, although the regions I and IV also exert a slight influence. Additionally, BT V200A and V200A/P258N possessed high hydrolase activity towards sucrose.
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PMID:Molecular determinants of substrate recognition in thermostable alpha-glucosidases belonging to glycoside hydrolase family 13. 1752 2


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