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PubMed1981

Study on the role of tyrosine side-chains at the active centre of emulsin beta-D-glucosidase.

The role of exposed tyrosine side-chains in enzyme-catalyzed reaction by sweet almond emulsin beta-D-glucosidase (beta-D-glucoside glucohydrolase, EC 3.2.1.21) has been studied using N-acetylimidazole as the specific reagent. The changes in activity, binding affinity and kinetic parameters (Km, V) as a result of acetylation of the phenolic hydroxyl groups have been determined. The acetylation increased the Km values of both beta-glucosidase and beta-galactosidase activities, whereas V remained unchanged. Similarly, the binding affinity for immobilized phenyl beta-D-glucopyranoside decreased appreciably. After the removal of the acetyl groups the enzyme regained 96% of the original activity. It is concluded that the tyrosine moieties, located in the active centre of the enzyme, have both glucoside and galactoside binding functions.

Acetylation↗
PubMed1983

Studies on sphingomyelinase and beta-glucosidase activities in Niemann-Pick disease variants. Phosphodiesterase activities measured with natural and artificial substrates.

Cultured fibroblasts were studied from 12 cases of Niemann-Pick disease group C. In 11, sphingomyelinase and glucocerebrosidase (and beta-glucosidase) activities were reduced to around 50% of those of controls. On isoelectric focusing, all 12 strains lacked sphingomyelinase activity in the major cathodic region (pI 8.0). The defect was also demonstrated with the artificial phosphodiester substrates bis(4-methylumbelliferyl) phosphate and 4-methylumbelliferyl pyrophosphate diester. In control fibroblasts and those heterozygous for types A or B or group C Niemann-Pick disease, the major sphingomyelinase peak electrofocused at pI 8.0. No direct interaction could be demonstrated by mixing experiments between group C Niemann-Pick extracts and those of type A disease or Gaucher disease. Profiles for beta-glucosidase activity appeared normal in Niemann-Pick group C fibroblasts. No reduction of sphingomyelinase or glucocerebrosidase activities was found in Niemann-Pick group C liver, nor any attenuation of cathodic sphingomyelinase activity in the affected tissue. Results suggest that sphingomyelinase expression differs in fibroblasts and liver. Enzyme defects associated with Niemann-Pick disease group C were only observed in cultured cells.

Fibroblasts↗
PubMed1983

Synthesis of alpha-amylase and alpha-glucosidase by membrane bound ribosomes from Bacillus licheniformis.

Alpha-glucosidase was membrane bound during exponential growth of Bacillus licheniformis but was released into the medium during stationary phase. It could be partially removed from exponential phase cells by washing with NaCl (0.5 M). Alpha-Amylase was exclusively extracellular and could not be detected in cells. Polysomes were prepared from exponential phase cells and separated into membrane bound and soluble fractions. In vitro chain completion and immunoprecipitation showed that alpha-glucosidase and alpha-amylase were synthesized by membrane bound and not by soluble ribosomes.

Amylases↗
PubMed1982

Kinetic study of the inhibition of the honeybee haemolymph apha-glucosidase in vitro by BAYe 4609, BAYg 5421 and BAYn 5595.

Three therapeutic inhibitors of vertebrate alpha-glucosidases recently assayed in research on diabetes control, show high inhibitory potencies towards the p-NP-alpha-D-glucosidase activity of honeybee haemolymph. BAYe 4609 is an allosteric V-type (pure non-competitive) inhibitor with: Ki congruent to K'i congruent to I50 congruent to 180 micro M; n = 1.17; ni = 1.15 BAYg 5421, an hydrolysis derivative of the former, is a mixed allosteric inhibitor with: Ki congruent to 0.17 micro M; K'i congruent to 0.85 micro M; I50 congruent to 0.38 micro M; n = 1.19; ni = 1.25. BAYn 5595 isd a pure competitive Michaelian inhibitor with: Ki = 15 micro M; I50 congruent to 23 micro M. All these properties reveal similarities to and differences from those of the natural inhibitors of the enzyme and analogies with their action on vertebrate enzymes. Accordingly, correlations have been emphasized between the structure and the activity of these inhibitors which finally lead to propositions of structures for new active molecules.

1-Deoxynojirimycin↗
PubMed1987

Syntheses of homologous omega-aminated 1-methoxyalkyl beta-D-glucopyranosides as potential beta-D-glucosidase inhibitors.

(R)- and (S)-2-Azido-1-methoxyethyl beta-D-glucopyranosides (16) and (17), (R)- and (S)-3-azido-1-methoxypropyl beta-D-glucopyranosides (18) and (19), (R,S)-4-azido-1-methoxybutyl beta-D-glucopyranoside (20), and (R,S)-5-azido-1-methoxypentyl beta-D-glucopyranoside (22) were synthesized from omega-substituted dimethyl acetals of acetaldehyde, propanal, butanal, and pentanal by trimethylsilyl triflate-catalysed transacetalation using 1-O-trimethysilyl 2,3,4,6-tetra-O-acetyl-beta-D-glucose (1) as acceptor. Most of the acetylated (R,S)-epimers could be resolved into pure compounds by column chromatography. Preliminary tests showed that the deacetylated acetal glucosides carrying omega-bromo, azido, or acetamido substituents in the aglycon are good substrates for beta-D-glucosidase from sweet almonds. The corresponding omega-amino derivatives of compounds 16, 19, 20, and 22, (R)-2-amino-1-methoxyethyl beta-D-glucopyranoside (23), (S)-3-amino-1-methoxypropyl beta-D-glucopyranoside (24), (R,S)-4-amino-1-methoxybutyl beta-D-glucopyranoside (25), and (R,S)-5-amino-1-methoxypentyl beta-D-glucopyranoside (26) proved almost completely resistant to beta-D-glucosidase. The stability of the glucosides against enzyme hydrolysis is dependent on the distance between the amino group and the anomeric center.

Alkylation↗
PubMed1979

Carbohydrate content of acid alpha-glucosidase (gamma-amylase) from human liver.

The presence of carbohydrates in homogeneous preparations of human liver acid alpha-glucosidase has been established and the carbohydrate content of the enzyme determined. The enzyme was purified with the specific purpose of removing all low-molecular-weight carbohydrates. It was specifically adsorbed on Concanavalin A-Sepharose, eluted with methyl-alpha-D-mannopyranoside and gave a positive reaction with the phenol-sulphuric acid reagent. These facts taken together provide evidence that the enzyme studied is a glycoprotein. The analysis of the carbohydrate content of human liver acid alpha-glucosidase showed that there were 8.3 glucosamine, 13.2 mannose and possibly 3--4 glucose residues per molecule of the enzyme with a molecular weight of 98,000.

Glucosamine↗
PubMed1991

Striking structural and functional similarities suggest that intestinal sucrase-isomaltase, human lysosomal alpha-glucosidase and Schwanniomyces occidentalis glucoamylase are derived from a common ancestral gene.

Sequence comparison of the primary structure of the yeast Schwanniomyces occidentalis glucoamylase (GAM) with GAMs in different microorganisms did not reveal significant similarities. By contrast, striking similarities were, surprisingly, found with 3 mammalian secretory and integral membrane proteins: the 2 subunits of intestinal brush border sucrase-isomaltase and human lysosomal alpha-glucosidase. The similarities among these proteins are found as clusters of up to 8 amino acids and distributed all over the protein sequences. The major sequence differences are found in the N-terminal regions accounting, probably, for the different cellular locations of these proteins. The high level of similarities between sucrase, isomaltase, Sch. occidentalis GAM and human lysosomal alpha-glucosidase suggest that these proteins are derived from the same ancestral gene. To our knowledge, this is the first report that describes similarities between a yeast secretory protein and mammalian secretory and integral membrane proteins.

Amino Acid Sequence↗
PubMedDate not supplied

Demonstration of acid alpha-glucosidase in different types of Pompe disease by use of an immunochemical method.

The nature of mutant acid alpha-glucosidase (AAG) in muscle was studied in 6 patients with Pompe disease, consisting of 2 each of the infantile, childhood and adult types. Anti-human liver AAG rabbit antibody prepared in the present study was confirmed to be monospecific by immunodiffusion, immunotitration and immunohistochemical methods. It was found by the immunodiffusion and enzyme immunoassay methods using this antibody that the mutation produced a normal amount of enzyme protein but the latter was an inactive form, suggesting structural gene mutation in 5 of the 6 cases. In the remaining childhood type case there was no detectable amount of enzyme protein, suggesting that the mutation causes a reduction in the amount of the enzyme protein or synthesis of unstable enzyme protein. Similarly, the enzyme activity of AAG was markedly reduced in all patients, but that of neutral alpha-glucosidase was the least reduced in the adult type, medium in the childhood type, and the most reduced in the infantile type.

Adult↗
PubMed1990

cDNA cloning and expression of a Talaromyces emersonii beta-glucosidase determinant in Escherichia coli.

Intact mRNA has been isolated from the thermophilic fungus Talaromyces emersonii following growth on lactose-containing media and this has been used as template to produce cDNA. This cDNA has been cloned into the Escherichia coli expression system, pUC18 and this DNA was used to transform E. coli. A 2.1 kb fragment was isolated and shown to encode functional beta-glucosidase activity in E. coli. When the fragment was sub-cloned into a leaky strain of E. coli K-12, beta-glucosidase activity was detected in culture supernatants. The fragment was characterised further using restriction enzyme analysis and was also used as a probe in Northern and Southern blotting analyses of T. emersonii mRNA and genomic DNA, respectively. Results obtained from these analyses verified that the cloned insert DNA was of T. emersonii origin.

Blotting, Northern↗
PubMed1996

Expression of cDNA-encoded human acid alpha-glucosidase in milk of transgenic mice.

Enzyme replacement therapy is at present the option of choice for treatment of lysosomal storage diseases. To explore the feasibility of lysosomal enzyme production in milk of transgenic animals, the human acid alpha-glucosidase cDNA was placed under control of the alpha S1-casein promoter and expressed in mice. The milk contained recombinant enzyme at a concentration up to 1.5 micrograms/ml. Enzyme purified from milk of transgenic mice was internalized via the mannose 6-phosphate receptor and corrected enzyme deficiency in fibroblasts from patients. We conclude that transgenically produced human acid alpha-glucosidase meets the criteria for therapeutic application.

Animals↗
PubMed1987

Human acid beta-glucosidase: use of inhibitors, alternative substrates and amphiphiles to investigate the properties of the normal and Gaucher disease active sites.

Comparative studies with lipoidal inhibitors and alternative substrates were conducted to investigate the properties of the active site of human acid beta-glucosidase (D-glucosyl-N-acylsphingosine glucohydrolase, EC 3.2.1.45) from normal placenta and spleens of Type 1 Ashkenazi Jewish Gaucher disease (AJGD) patients. With the normal enzyme, the inhibitory potencies of series of alkyl(Cn; n = 0-18)amines, alkyl beta-glucosides and alkyl-1-deoxynojirimycins were a biphasic function of increasing chain length: i.e., large decreases in Ki,app or IC50 were found only with n greater than 4 and limiting values were approached with n = 12-14. This biphasic function of alkyl chain length was observed in the presence or absence of detergents and/or negatively charged lipids. In the presence of Triton X-100 concentrations greater than the critical micellar concentration, the relative (to deoxynojirimycin) inhibitory potencies of the N-Cn-deoxynojirimycins (n greater than 4) were decreased about 3-5-fold, due to an energy requirement to extract the inhibitors from Triton X-100 micelles. The Ki,app or IC50 of N-hexylglucosylsphingosine was inversely related to the Triton X-100 concentration and was not affected by the presence of 'co-glucosidase'. The mutual exclusion of glucon, N-Cn-deoxynojirimycin and sphingosine derivatives from the normal enzyme suggested a shared region for binding in the active site. Increasing the fatty-acid acyl chain length of glucosyl ceramide from 1 to 24 carbons had minor effects on Km,app ( = Kis,app) (8-40 microM), but increased Vmax,app up to 13-fold. With the AJGD enzyme, the inhibitor and alternative substrate findings were similar to those with the normal enzyme, except that Kis,app(AJGD)/Kis,app(normal) = 4 to 11 for the Cn-glycons and sphingosine derivatives. These results indicated that (1) the Ki,app or Km,app values for amphiphilic inhibitors or substrates reflect a balance of binding energies for two hydrophobic subsites within the enzyme's active site and Triton X-100 micelles and (2) the abnormal properties of the AJGD enzyme result from an amino-acid alteration(s) within or near a hydrophilic region which is shared by the glycon-binding site and the two hydrophobic sites of the active site.

1-Deoxynojirimycin↗
PubMedDate not supplied

A stepwise approach to the understanding of extracellular enzyme activity in soil. II. Competitive effects on the adsorption of a beta-D-glucosidase in mixed mineral or organo-mineral systems.

A previous study has shown the effect of individual mineral surfaces on the activity of sweet almond beta-D-glucosidase. We now consider more complex situations likely to occur in soil, such as adsorption onto mixtures of different mineral surfaces, and the effect on enzyme activity of mineral surfaces with organic coatings. The effect of the order of addition of the minerals to enzyme suggests that the rate of adsorption is limited by the diffusion of the protein towards the interface and is not influenced by the magnitude of attractive forces between the protein and the surface. Adsorption is found to be quasi-irreversible. A study of the effect of artificial coatings of montmorillonite on enzyme activity led to the conclusion that an exchange of the enzyme with molecules of the coating occurs. This exchange is dependent upon the adsorption energy of the molecules of the coating and the electric charge of beta-D-glucosidase. This model is used for the interpretation of the effect of natural clay-humic complexes on enzyme activity.

Adsorption↗
PubMed1982

Canine glycogen storage disease type II. A biochemical study of an acid alpha-glucosidase-deficient Lapland dog.

A biochemical study was performed in a Lapland dog suspected of glycogen storage disease type II (acid alpha-glucosidase deficiency, Pompe's disease). Glycogen content was substantially elevated in heart and skeletal muscle but not in the liver. Severely reduced activities of acid alpha-glucosidase (EC 3.2.1.20) were found in heart, skeletal muscle, liver and cultured tongue fibroblasts. The deficiency was located in the glycoprotein fraction, which supported its lysosomal origin. The electrophorogram showed after acid incubation that the affected dog was missing the activity band, while after neutral incubation the pattern was similar to control. The obtained biochemical data are compared with the known data of the human pathology.

Animals↗
PubMed1988

Purification of the beta-glucosidase from Sclerotinia sclerotiorum.

A beta-glucosidase (EC 3.2.1.21) has been isolated from culture filtrates of the fungus Sclerotinia sclerotiorum. The protein was purified by gel filtration on a column of Bio-Gel P-300 and by ion exchange chromatography on DEAE-Bio-Gel A. The molecular weight, determined by gel filtration, was 240,000. Km values for the enzyme towards p-nitrophenyl-beta-D-glucoside and cellobiose were respectively 0.10 mM and 1.23 mM. The beta-glucosidase activity was found to be strongly associated with a beta-xylosidase (EC 3.2.1.37) activity, suggesting that both activities could be represented in a single protein complex.

Ascomycota↗
PubMed1990

Purification and properties of a beta-glucosidase from Penicillium oxalicum autolysates.

A beta-glucosidase from the medium of an autolyzed culture of Penicillium oxalicum has been purified by tannic acid precipitation, sephacryl S-200, DEAE-Biogel, CM-Biogel and Mono Q successively. The purification process produced a homogeneous band in the SDS-PAGE that correspond to a Mr of 133,500. The enzyme had a pl of 4, and the active optima were found at pH 5.5 and 55 degrees C. The enzyme hydrolyzed different substrates showing maximum affinity against p-nitrophenyl-beta-D-glucoside with a Km value of 0.37 mM. The beta-glucosidase was inhibited by Glucono-D-lactone but not by glucose in the concentration range of 1 to 10 mM. The enzyme was adsorbed by Concanavalin-A-Sepharose.

Glucosidases↗
PubMed1983

Differential effects on the cyanogenic glycoside content of fermenting cassava root pulp by beta-glucosidase and microbial activities.

The degradation of cyanogenic glycosides was studied in spontaneously fermenting cassava root pulp and in fresh pulp samples pretreated to prevent either endogenous beta-glycosidase activity, fermentation, or both. The rate of disappearance of the glycosides, as measured by hydrocyanic acid (HCN) production in situ, in membrane-sterilised media or in samples containing 1% sodium iodoacetate, was comparable with the untreated control in which 85% of the substrate was broken down within 72 h. Pretreatment of the fresh pulp with the beta-glucosidase inhibitor 1,5-gluconolactone (1%) markedly reduced the rate of disappearance of the cyanogens while inclusion of glucose in this test medium at the 3% level appeared to induce some hydrolysis. Loss of bound (glycosidic) cyanide in sterilised medium containing the glucosidase inhibitor was negligible. The results suggest that the contribution of the fermentation process in cyanide detoxification of pulped cassava roots is minimal.

Cyanides↗
PubMed2004

Glycogenosis type II: identification and expression of three novel mutations in the acid alpha-glucosidase gene causing the infantile form of the disease.

Glycogenosis type II (GSDII) is an autosomal recessive disorder due to the deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). We identified three novel point mutations, C399A, T1064C, and C2104T, in three unrelated Italian patients with the infantile form of the disease. The C399A mutation was present in homozygosity in proband 1. The C >A transition introduces a premature stop signal in exon 2 resulting in no enzyme production that is correlated with the severe clinical phenotype in this patient. The other two nucleotide changes were missense mutations. The T1064C mutation, which changes Leu in position 355 into Pro, was carried in homozygosity by proband 2. The C2104T nucleotide change, which substitutes Arg 702 into Cys, was present in proband 3 in combination with a known severe mutation DeltaI17-18. The in vitro expression in COS-1 cells of T1064C and C2104T constructs demonstrated no enzymatic activity with respect to the negative control cells. Western blot analysis revealed that both T1064C and C2104T mutant proteins produced in COS-1 cells migrated in SDS-PAGE as the GAA inactive precursor of 110kDa. Immunofluorescence detection of mutant alpha-glucosidases showed enzyme localization primarily in the ER-Golgi compartment, suggesting that T1064C and C2104T mutations could affect the normal processing and stability of the enzyme. In vitro studies demonstrated that the same degree of deficiency in T1064C and C2104T mutations, which is in contrast with patient phenotype. A better correlation was observed with the in vivo studies since proband 2, with a less severe phenotype, presented with low residual enzyme activity while in proband 3, with a classic severe infantile onset GSDII, fibroblast enzyme activity was completely absent.

Animals↗
PubMed1988

Solubilization of membrane-bound acid alpha-glucosidase by proteolysis.

The membrane-bound acid alpha-glucosidase was purified partially (400-fold) from human placenta by solubilization with trypsin, concanavalin A-Sepharose chromatography, Ultrogel AcA-34 gel filtration, and Sephadex G-100 affinity chromatography. Two molecular forms of the enzyme were found in the final preparation of the purified enzyme. They were identical in molecular weight with a precursor (110 kDa) and an early intermediate form (105 kDa) of this enzyme. Also direct incubation of the membrane fraction without trypsin resulted in a release mainly of the 105 kDa form, which was inhibited by N-ethylmaleimide, but not by leupeptin, pepstatin or phenylmethylsulfonylfluoride. It was concluded that the precursor of acid alpha-glucosidase is an intrinsic membrane protein, which is transported into lysosomes after solubilization by proteolysis.

Ethylmaleimide↗