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At least 649 records · Page 36Linked to original sources
PubMed1987

Effect of Increased beta-Glucosidase Activity on Virulence of Erwinia amylovora.

Plant tissues often contain beta-glucosides that can be enzymatically hydrolyzed to produce toxic aglycones. It has been suggested that the low beta-glucosidase activity found in Erwinia amylovora contributes to bacterial virulence by allowing the bacteria to infect plants that contain beta-glucosides without inducing the formation of toxic aglycones. To test this suggestion, we created strains of E. amylovora which had high beta-glucosidase activities and studied the ability of these strains to cause fire blight disease in pears (Pyrus communis). We isolated spontaneous mutants that were able to utilize beta-glucosides as the sole carbon source and showed that one class had about 10 times as much beta-glucosidase activity as the wild-type strain. In addition, we constructed several plasmids that carry the Escherichia coli bgl operon under the control of a transposon Tn5 promoter that is expressed in E. amylovora. These plasmids were introduced in E. amylovora by transformation. Pathogenesis studies in immature Bartlett pear fruits, etiolated sprouts, and young shoots showed that a 100-fold increase in beta-glucosidase activity does not interfere with normal development of fire blight disease in these model systems.

Journal Article↗
PubMed1993

Localization and Characterization of alpha-Glucosidase Activity in Brettanomyces lambicus.

Brettanomyces lambicus was isolated and identified from a typical overattenuating Belgian lambic beer and exhibited extracellular and intracellular alpha-glucosidase activities. Production of the intracellular enzyme was higher than production of the extracellular enzyme, and localization studies showed that the intracellular alpha-glucosidase is mostly soluble and partially cell wall bound. Both intracellular and extracellular enzymes were purified by ammonium sulfate precipitation, gel filtration (Sephadex G-150, Sephadex G-200, Ultrogel AcA-44), and ion-exchange chromatography (sulfopropyl-Sephadex C-50, (carboxymethyl-Sephadex C-50). The intracellular alpha-glucosidase exhibited optimum activity at 39 degrees C and pH 6.2. The extracellular enzyme exhibited optimum catalytic activity at 40 degrees C and pH 6.0. The molecular masses of purified intracellular and extracellular alpha-glucosidases, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were 72,500 and 77,250, respectively. For both enzymes there was a decrease in the rate of hydrolysis with an increase in the degree of polymerization, and both enzymes hydrolyzed dextrins isolated from lambic wort (degrees of polymerization, 3 to 9 and more than 9). The K(m) values for p-nitrophenyl-alpha-d-glucopyranoside, maltose, and maltotriose for the intracellular enzyme were 0.9, 3.4, and 3.7 mM, respectively. The K(i) values for both enzymes were between 28.5 and 57 muM for acarbose and between 7.45 and 15.7 mM for Tris. These enzymes are probably involved in the overattenuation of spontaneously fermented lambic beer.

Journal Article↗
PubMedDate not supplied

The effect of an alpha-glucosidase inhibitor and insulin on glucose metabolism and lipid profiles in non-insulin-dependent diabetes mellitus.

Studies were carried out to assess various ways of improving glycaemic control and lipid profiles of patients with noninsulin-dependent diabetes mellitus (NIDDM) in whom glucose metabolism was poor. Part or all of the dose of the sulphonylurea that had been used to treat patients in Group 1 (n = 8) was replaced by an alpha-glucosidase inhibitor. Symptoms related to hypoglycaemia disappeared and the postprandial blood glucose level was significantly increased (P < 0.043) but serum lipid levels were not significantly altered and the mean glycosylated haemoglobin level was unchanged. In Group 2 (n = 10) patients, a large part of the insulin dose was replaced by an alpha-glucosidase inhibitor. Hypoglycaemia-related symptoms disappeared but there were no significant changes in lipid profiles, postprandial blood glucose or glycosylated haemoglobin levels. The third group of patients (n = 9) had been treated with insulin alone and were given additional alpha-glucosidase inhibitor without changing their insulin dose. This did not significantly change their lipid profiles, postprandial blood glucose or glycosylated haemoglobin levels. In Group 4 (n = 9) the addition of an alpha-glucosidase inhibitor to the initial sulphonylurea did not produce any significant changes in mean postprandial blood glucose or glycosylated haemoglobin levels. The results for individual patients indicated that the glycosylated haemoglobin levels had improved after the change of treatment only in those patients whose connective peptide immunoreactivity was > or = 6.0 ng/ml.

Aged↗
PubMed1994

Pharmacology of alpha-glucosidase inhibition.

The development of alpha-amylase and brush-border alpha-glucosidase inhibitors is reviewed. The mode of action as well as pharmacological and pharmacodynamic properties of selected inhibitors with special regard to the most thoroughly investigated alpha-glucosidase inhibitor acarbose are discussed. Inhibition of intestinal alpha-glucosidases delays the digestion of starch and sucrose, flattens the postprandial blood glucose excursions, and thus mimics the effects of dieting on hyperglycaemia, hyperinsulinaemia and hypertriglyceridaemia. Therefore, the mechanism of alpha-glucosidase inhibition represents the pharmacological optimization of the dietary principle of delayed carbohydrate absorption. In pre-clinical studies using diabetic animals the oral administration of acarbose improved the metabolic state and reduced the blood glucose area under the curve. As a consequence, the process of non-enzymatic glycation of proteins was retarded as indicated by reduced glycated haemoglobin, glomerular basement membranes or advanced glycation end-products (AGEs) in collagen. These improved biochemical parameters correlated with beneficial effects against the development of diabetic nephropathy and neuropathy. Thus, the treatment of diabetic animals with acarbose does not only improve the metabolic state but has also the potential to delay, or possibly prevent, the development of diabetic complications.

1-Deoxynojirimycin↗
PubMedDate not supplied

[A comparative study of the effect of inhibitors of microbial origin on different alpha-glucosidases].

The action of a new alpha-glucosidase inhibitor from Streptomyces sp. and Acarbose on alpha-glucosidases of various origins has been studied. Differences in specificity, efficiency, nature and type of inhibition of microbial glucosidases and some enzymes of the small intestine mucosa by the biologically active substances studied were revealed. At certain concentrations these inhibitors can be substrates for some intestinal glucosidases. It is suggested that the inhibitor from Streptomyces sp. (in combination with a diet) can be used for regulation of some disturbances in carbohydrate metabolism.

Acarbose↗
PubMed2004

Twenty-two novel mutations in the lysosomal alpha-glucosidase gene (GAA) underscore the genotype-phenotype correlation in glycogen storage disease type II.

Patients with glycogen storage disease type II (GSDII, Pompe disease) suffer from progressive muscle weakness due to acid alpha-glucosidase deficiency. The disease is inherited as an autosomal recessive trait with a spectrum of clinical phenotypes. We have investigated 29 cases of GSDII and thereby identified 55 pathogenic mutations of the acid alpha-glucosidase gene (GAA) encoding acid maltase. There were 34 different mutations identified, 22 of which were novel. All of the missense mutations and two other mutations with an unpredictable effect on acid alpha-glucosidase synthesis and function were transiently expressed in COS cells. The effect of a novel splice-site mutation was investigated by real-time PCR analysis. The outcome of our analysis underscores the notion that the clinical phenotype of GSDII is largely dictated by the nature of the mutations in the GAA alleles. This genotype-phenotype correlation makes DNA analysis a valuable tool to help predict the clinical course of the disease.

Adolescent↗
PubMedDate not supplied

Similar biochemical properties of human seminal plasma and epididymal alpha-1,4-glucosidase.

We have studied some characteristics of alpha-1,4-glucosidases in human male reproductive organs in order to obtain information on the origin of the enzyme in seminal plasma. Acid and neutral enzymes could be distinguished on the basis of their selective inhibition either by SDS (acid enzyme) or MTT (neutral enzyme). Only the epididymis contained a significant amount of SDS resistant neutral alpha-1,4-glucosidase which was comparable to what has been isolated in seminal plasma. The similarity of epididymal and seminal plasma neutral enzymes was further confirmed by ultracentrifugation on sucrose density gradients, which permitted a complete separation of neutral (11S) and acid (4S) iso-enzymes. The 11S form was present in epididymis and in seminal plasma, but was totally absent in seminal vesicles, prostates and testis. The epididymal enzyme also had some of the unique characteristics found in the seminal plasma enzyme: it precipitated upon dialysis against distilled water, and its mobility on SDS polyacrylamide gel electrophoresis was identical to that of form 1 in seminal plasma. These results, although they do not constitute absolute proof of the identity of epididymal and seminal plasma alpha-glucosidase, certainly provide strong support for this hypothesis.

Adult↗
PubMed1988

The promoter of the beta-glucosidase gene from Kluyveromyces fragilis contains sequences that act as upstream repressing sequences in Saccharomyces cerevisiae.

The relationship between the promoter length of the Kluyveromyces fragilis beta-glucosidase gene and the level of its expression in Saccharomyces cerevisiae was studied by gene fusion between deleted promoter fragments of various lengths and the promoterless beta-galactosidase gene of Escherichia coli. The removal of a region from position -425 to -232 led to a tenfold increase in the expression of the gene. The same results were obtained for the reconstructed beta-glucosidase gene with the same promoter length. It is likely that the deletion of this part of the promoter removes negative regulatory elements which are functional in Saccharomyces cerevisiae. This increase in activity is the main event which may explain the high increase in gene expression (60-fold) previously observed for an upstream deletion obtained during subcloning experiments of the beta-glucosidase gene. It is also shown that the expression of the gene greatly depends upon the nature of the recipient strain, the growth phase of the cell and that of the vector carrying it.

Base Sequence↗
PubMed1986

Biosynthesis regulation of the beta-glucosidase produced by a yeast strain transformed by genetic engineering.

The biosynthesis of the beta-glucosidase enzyme was studied in a transformed yeast obtained by cloning in Saccharomyces cerevisiae the structural gene coding for beta-glucosidase in Kluyveromyces fragilis. The enzyme biosynthesis was found to be non-adaptative, and repressed by glucose. These features are similar to those observed in K. fragilis. beta-Glucosidase activity in the transformed yeast was much higher than in K. fragilis. We attempted to ferment cellobiose with the transformed yeast: practically no cellobiose was consumed, growth and ethanol production were negligible. Warburg experiments showed that cellobiose fermentation did not occur when the respiratory chain was not functioning.

Cellobiose↗
PubMed1987

Sequence and transcription of the beta-glucosidase gene of Kluyveromyces fragilis cloned in Saccharomyces cerevisiae.

The complete nucleotide sequence of the beta-glucosidase gene of Kluyveromyces fragilis has been determined. This sequence contains an open reading frame of 2535 base pairs encoding a protein of 845 amino acids. Analysis of the transcription products revealed only one transcript of about 3 kb identical in both Kluyveromyces fragilis and in the expression host Saccharomyces cerevisiae. The protein molecular weight of 93,811 Kd deduced from the sequence is consistent with the 90,000 Kd determined by SDS polyacrylamide gel electrophoresis with the purified protein. Mapping of the starts of transcription shows that two starting points are used in the natural host Kluyveromyces fragilis. A comparison of the amino acid sequence with that of other beta-glucosidases revealed three regions of homology. One of these regions contains an amino acid sequence very similar to a peptide isolated from the active site of beta-glucosidase A3 from Aspergillus wentii and could be implicated in the catalytic mechanism of these glucolytic enzymes.

Amino Acid Sequence↗
PubMed1994

[The decomposition of Maillard reaction products by amylolytic enzymes. 1. Reversible inhibition of alpha- and glucoamylase and alpha-glucosidase by oligosaccharide Amidori compounds].

The influence of Amadori-compounds (fructosyl-, maltulosyl- and maltotriulosylglycin) on the activity of the enzymes alpha-glucosidase (from Saccharomyces cerevisiae), glucoamylase (from Aspergillus niger) and alpha-amylase (from porcine pancreas) was studied. Fructosylglycin was not hydrolyzed by all three enzymes. alpha-Glucosidase hydrolyzes maltulosylglycin 10 times slower than maltotriulosylglycin. Glucoamylase and alpha-amylase catalyze only the cleavage of maltotriulosylglycin to form glucose and maltulosylglycin. The activities of alpha-glucosidase and glucoamylase are inhibited through the Amadori-compounds fructosyl- and maltulosylglycin. These Amadori-compounds don't influence the activity of alpha-amylase. Electronic effects or interactions between the secondary amino function of Amadori-compounds and the carboxyl- or carboxylate groups of active centres could be responsible for such an inhibition.

Animals↗
PubMed1985

Gaucher disease (type 1): physical and kinetic properties of liposomal and soluble 'acid' beta-glucosidase.

'Acid' beta-glucosidase of human spleen, from either normal controls or patients with type 1 (adult) Gaucher disease, was incorporated into phosphatidylcholine liposomes. The non-incorporated (soluble) Gaucher-enzyme had a higher apparent molecular weight than had the corresponding control. Liposomal 'acid' beta-glucosidase prepared from Gaucher-spleen was more thermostable than was the corresponding normal enzyme; it was also stimulated by acidic lipids to a much lesser extent. The results suggest that the genetic mutation in type 1 (adult) Gaucher disease has multiple effects on the glycoprotein form of 'acid' beta-glucosidase.

Cell Membrane↗
PubMed1983

Induction of beta-D-glucosidase in Streptomyces granaticolor.

beta-D-glucosidase in Streptomyces granaticolor is an inducible enzyme. Methyl-beta-D-glucoside or cellobiose, added to a glycerol-containing medium, are most suitable inducers. The activity of beta-D-glucosidase in a culture fully induced by cellobiose is 50 times higher than the basal level of the enzyme. beta-D-glucosidase is an intracellular enzyme, whose inducibility differ with culture age and reaches its maximum in a 10-h-old mycelium. The enzyme synthesis begins 2 h after the addition of the induced and reaches its maximum after a 10-h-induction.

Cell-Free System↗
PubMed1982

Influence of pH on the formation and location of beta-glucosidase in Aspergillus terreus grown on ceLlulose.

Wild strain of Aspergillus terreus is very good producer of beta-glucosidase. It produces 15 nkat/mL (0.9 IU/mL) of extraceLlular beta-glucosidase at pH 5.0. The medium pH level strongly affects the production and binding of beta-glucosidase on the cells and on residual cellulose. At pH 4.0 the rate of enzyme synthesis and the level of total activity is highest but 60-75% of this activity is bound. At higher pH levels the enzyme is mainly released to the medium.

Aspergillus↗
PubMed2005

Cloning and expression of a gene for an alpha-glucosidase from Saccharomycopsis fibuligera homologous to family GH31 of yeast glucoamylases.

Cloning of cDNA encoding an alpha-glucosidase from the dimorphous yeast Saccharomycopsis fibuligera and characterization of the gene product were performed. The cDNA of the putative alpha-glucosidase gene consists of 2,886 bp, which includes an open reading frame encoding a 19 amino acid signal peptide at the N-terminal end and a 944 amino acid mature protein with a predicted molecular mass of 105.4 kDa and pI value of 4.52. The deduced amino acid sequence shows a high degree of identity (70%) with two yeast glucoamylases, namely, the extracellular glucoamylase Gam from Schwanniomyces occidentalis and the cell surface glucoamylase Gca from Candida albicans. The recombinant product, synthesized in Saccharomyces cerevisiae, is localized on the cell surface and hydrolyses maltooligosaccharides exclusively without the ability to digest soluble starch, which is consistent with the specificity characteristic of alpha-glucosidase, EC. 3.2.1.20.

Amino Acid Sequence↗
PubMed1984

Human lysosomal beta-glucosidase: purification by affinity chromatography.

Two Sepharose-bound substrate analogs, 6'-aminohexanoyl-(2-N-sphingosyl-O-beta-D-glucoside) and 6'-aminohexyl-dodecanedioyl-1-(2-N-sphingosyl-1-O-beta-D-glu coside), were synthesized and used sequentially for the affinity purification of lysosomal beta-glucosidase (N-acyl-sphingosyl-1-O-beta-D-glucoside:glucohydrolase, EC 3.2.1.45). The capacities of these nondegradable affinity supports were 0.1 and 0.15 mg enzyme/ml settled gel, respectively. The purified enzyme had a specific activity of 75 mumol min-1 mg-1. The preparation had a single protein band with a molecular weight of 67,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, evidencing its apparent homogeneity. Isoelectric focusing on granular gels revealed four molecular forms of the enzyme with pI values of 4.0, 4.5, 4.7, and 5.8 to 6.2. The purified enzyme hydrolyzed glucosyl ceramide and 4-methylumbelliferyl-beta-D-glucoside with Km and Vmax values of 0.6 and 2.5 mM, and 101 and 26.1 mumol min-1 mg-1, respectively. The enzyme also hydrolyzed octyl beta-glucoside, a linear mixed-type inhibitor of the enzyme. Binding constants (Ki) were determined for the inhibitors, sphingosyl-1-O-beta-D-glucoside (Ki = 20 microM) and its N-hexyl derivative (Ki = 0.3 microM). The enzyme had a half-life of 65 and 30 min at 50 degrees C and pH 5.0 or 6.0, respectively. In addition, two other classes of ligands were used for the purification of lysosomal beta-glucosidase, and their capacities and specificities were compared to those of the substrate analog affinity supports. These included (i) the alkyl amine inhibitors octylamine, decylamine, and tetradecylamine; and (ii) the inhibitors, 6-aminohexanoyl-beta-glucosylamine and aminododecanoyl-1-(2-N-sphingosyl-1-O-beta-D-glucoside). Compared to these other ligand columns, the substrate analog affinity supports had about 100- to 1000-fold greater capacities or afforded 8- to 40-fold greater purification of human lysosomal beta-glucosidase.

Chromatography, Affinity↗
PubMed1984

Further studies of the structure of human placental acid alpha-glucosidase.

Acid alpha-glucosidase has been purified from human placenta to a specific activity of approximately 6800, (4-methylumbelliferyl-alpha-D-glucoside as a substrate) or 55,400 mumol g-1 min-1 (glycogen or maltose as substrate). The purified enzyme gives rise to multiple protein bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), i.e., a major doublet of 82K and 69K , a minor doublet of 25K and 21K , and a faint band of 100K. All of the molecular weight species stained as glycoproteins with an intensity apparently proportional to their protein content, and were present in enzyme from individuals homozygous for the allozyme alpha-Glu 1. Isoelectric focusing revealed only enzymatically active proteins which, when analysed by SDS-PAGE, gave rise to multiple molecular weight species. Chromatography of I125-labeled, purified enzyme on Bio-Gel P-100 revealed only a radiolabeled, high-molecular-weight species which corresponded with enzyme activity. These findings suggest that, in the native state, the mature enzyme exists as a high-molecular-weight species, which is dissociable in SDS to several low-molecular-weight species. These results are consistent with reports that a 100K primary product of translation is post-translationally modified to yield polypeptides of lower molecular weights, and that all of the molecular species are absent in cells genetically deficient for acid alpha-glucosidase. The possibility that the low-molecular-weight (20- 25K ) protein bands in SDS-gels corresponded to a previously reported low-molecular-weight species generated by treatment with guanidine-HCl was investigated. The I125-labeled, purified acid maltase was dissociated by guanidine into two equal peaks of approximately 64K and 28K molecular weight. Surprisingly, both peaks, when analyzed on SDS-gels, yielded identical and equally intensely staining bands of 64K molecular weight. These results suggest that the mature acid alpha-glucosidase is made up of polypeptides which are bonded in the native state by at least two different types of interaction, one type which is dissociable in SDS and one type which is dissociable in guanidine but not in SDS. The nature and possible function of the 25K polypeptide generated only by guanidine-HCl remains to be determined.

Chemical Phenomena↗
PubMed1985

Purification and characterization of the extracellular beta-glucosidase produced by Candida wickerhamii.

Candida wickerhamii NRRL Y-2563 produced a cell-bound beta-glucosidase when grown in complex media containing 50 g of cellobiose per liter. The majority of the enzyme was located on the cell surface and was released into the supernatant upon treatment of intact cells with Zymolyase 60,000. Only about 10% of the total activity was associated with the cytoplasm. The enzyme was purified to homogeneity, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme had an apparent native molecular mass of about 198,000 Da and appeared to be composed of two subunits with approximate molecular masses of 94,000 Da. The beta-glucosidase contained approximately 30.5% (w/w) carbohydrate. Mannose was the only detected neutral carbohydrate associated with the purified enzyme. The enzyme demonstrated optimal activity at a pH of 4.0 to 5.0. The Km of the purified beta-glucosidase was 6.74 X 10(-2) M for cellobiose and 4.17 X 10(-3) M for p-nitrophenyl-beta-D-glucopyranoside. Glucose did not appear to inhibit the enzyme.

Amino Acids↗