Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.21 (beta-glucosidase)
 3,280 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This enzyme shows beta-D-glucosidase, beta-D-fucosidase and beta-D-galactosidase activities, all associated in a single peak in Sephadex G-200, DEAE-cellulose, concanavalin A-Sepharose chromatographies, and in high resolution isoelectric focusing (pI 4.56), having the optimal pH in the range 4.5-5.5. The enzyme is very stable under different conditions: (i) at pH in the range 5.5-7.0; (ii) in successive freezing-thawing cycles; (iii) at 4 degrees C; (iv) after exhaustive ultrasonic treatment. It is not stable beyond 40 degrees C, and in the presence of urea, Triton X-100, SDS or mercaptoethanol. HgCl2, KCN, Tris, maltose and the lactones were inhibitors of the enzyme. With glucose, fucose and galactose the inhibition is competitive. In addition, a transglycosylation mechanism seems to occur. The kinetic studies suggest a substrate-activation model and the presence of two primary active sites: fuco-gluco and galacto.
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PMID:Characterization and kinetics of beta-D-gluco/fuco/galactosidase from sheep liver. 641 26

An inducible endo-beta-1,6-glucanase was purified from Penicillium brefeldianum by DEAE-cellulose, Bio-Gel P-150 and high-pressure liquid chromatography. The final preparation was essentially free from beta-1,3-glucanase and beta-glucosidase activities. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis revealed one protein band with an Mr of 44000. The Vmax. and Km values were calculated to be 624 units (mumol/min)/mg and 2.78 mg/ml respectively. The glucanase had lytic activity against mycelial cells of the yeast Candida albicans. The yield of purified beta-1,6-glucanase from 100 mg dry weight of freeze-dried culture filtrate varied from 60 to 180 units.
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PMID:Purification and properties of a beta-1,6-glucanase from Penicillium brefeldianum. 650 37

Polyacrylamide gel electrophoresis of the cellulolytic system from culture supernates of Acetivibrio cellulolyticus showed the presence of four major enzymes: a beta-glucosidase, an exoglucanase, and two endoglucanases. The relative proportions of these enzymes in the culture supernate were affected by the nature of the cellulosic substrate and by the length of the incubation period. The molecular weights of the cellulolytic enzymes were beta-glucosidase, 81 000; exoglucanase, 38 000; endoglucanase C2, 33 000; and endoglucanase C3, 10 400, as estimated by their electrophoretic mobilities relative to proteins of known molecular weight. Treatment of the high molecular weight endoglucanase with SDS--mercaptoethanol led to reversible dissociation of the enzyme into polypeptide subunits similar to the low molecular weight endoglucanase. Endoglucanase activity could be assayed for directly using a novel method of incorporating carboxymethyl cellulose in the polyacrylamide gels. The molecular weights and functions of these enzymes are compared with those detected in culture filtrates of various fungi.
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PMID:Cellulolytic enzyme system of Acetivibrio cellulolyticus. 678 18

beta-D-Mannosidase (beta-D-mannoside mannohydrolase EC 3.2.1.25) was purified 160-fold from crude gut-solution of Helix pomatia by three chromatographic steps and then gave a single protein band (mol. wt. 94,000) on SDS-gel electrophoresis, and three protein bands (of almost identical isoelectric points) on thin-layer isoelectric focusing. Each of these protein bands had enzyme activity. The specific activity of the purified enzyme on p-nitrophenyl beta-D-mannopyranoside was 1694 nkat/mg at 40 degrees and it was devoid of alpha-D-mannosidase, beta-D-galactosidase, 2-acetamido-2-deoxy-D-glucosidase, (1 leads to 4)-beta-D-mannanase, and (1 leads to 4)-beta-D-glucanase activities, almost devoid of alpha-D-galactosidase activity, and contaminated with less than 0.02% of beta-D-glucosidase activity. The purified enzyme had the same Km for borohydride-reduced beta-D-manno-oligosaccharides of d.p. 3-5 (12.5mM). The initial rate of hydrolysis of (1 leads to 4)-linked beta-D-manno-oligosaccharides of d.p. 2-5 and of reduced beta-D-manno-oligosaccharides of d.p. 3-5 was the same, and o-nitrophenyl, methylumbelliferyl, and naphthyl beta-D-mannopyranosides were readily hydrolysed. beta-D-Mannobiose was hydrolysed at a rate approximately 25 times that of 6(1)-alpha-D-galactosyl-beta-D-mannobiose and 6(3)-alpha-D-galactosyl-beta-D-mannotetraose, and at approximately 90 times the rate for beta-D-mannobi-itol.
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PMID:beta-D-Mannosidase from Helix pomatia. 683 86

Previous studies have shown that Biomphalaria glabrata contains a complete cellulolytic system which includes an endoglucanase, an exoglucanase and a beta-glucosidase. In the present report, a scheme for the purification of the endoglucanase from this invertebrate is proposed. Two major problems were encountered during the study: 1) the presence of a green-brownish pigment, which could not be eliminated by thermal shock or ammonium sulfate precipitation and 2) relative instability of enzymatic activity. Various alternatives were tested and the best sequence of steps was: 1) a sample of the crude extract, obtained by homogenization of the digestive glands in 50 mM Tris-HCl buffer, pH 8.4, and ultracentrifugation, was applied to a Q-Sepharose FPLC column (50 mM Tris-HCl buffer, pH 8.4; 10 mm x 22.2 cm column; flow rate 1.5 ml/min; 0.1 to 0.5 M NaCl gradient); 2) the eluate peak containing activity was dialyzed, lyophilized and eluted from a Superdex-75 gel filtration FPLC column (50 mM ammonium acetate buffer, pH 4.8; 16 mm x 60 cm column; flow rate 1.0 ml/min). A low degree of purification (about 36-fold) and recovery (about 12%) were observed, probably due to enzyme instability. SDS-electrophoresis of the active fraction showed a major peak of 30 kDa. In order to improve the purification scheme, further studies are required to stabilize this enzyme during purification and storage.
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PMID:Partial purification of an endoglucanase from Biomphalaria glabrata. 754 74

The ability of yeasts to ferment cellodextrins is rare. Candida wickerhamii is able to use these sugars for alcohol production because of a cell-bound, extracellular, beta-glucosidase that is unusual by not being inhibited by glucose. A cDNA expression library in lambda phage was prepared with mRNA isolated from cellobiose-grown C. wickerhamii. Immunological screening of the library with polyclonal antibodies against purified C. wickerhamii cell-bound, extracellular beta-glucosidase yielded 12 positive clones. Restriction endonuclease analysis and sequence data revealed that the clones could be divided into two groups, bglA and bglB, which were shown to be genetically distinct by Southern hybridization analyses. Efforts were directed at the study of bglB since it appeared to code for the cell-bound beta-glucosidase. Sequence data from both cDNA and genomic clones showed the absence of introns in bglB. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting of cell lysates from Escherichia coli bglB clones confirmed the presence of an expressed protein with an apparent molecular mass of 72 kDa, which is consistent with that expected for an unglycosylated form of the enzyme. Amino acid comparisons of BglB with other beta-glucosidase sequences suggest that it is a member of family 1 glycosyl hydrolases but is unusual in that it contains an additional 100 to 130 amino acids at the N terminus. This sequence did not have homologies to other known protein sequences and may impart unique properties to this beta-glucosidase.
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PMID:Cloning and characterization of a gene encoding a cell-bound, extracellular beta-glucosidase in the yeast Candida wickerhamii. 757 90

Differential gene expression at the transcriptional level was examined as an initial step in the investigation of the P(i) starvation response of Brassica nigra suspension cells. Total RNA was extracted from 7-day old cells grown in media containing either no P(i), 1.25 mM or 10 mM Pi. In vitro translation was carried out using their respective poly(A)+ RNA isolates and the resultant polypeptides were separated on a high-resolution SDS-PAGE gel. Scanning densitometry identified four polypeptides (ca. 31.7, 32.3, 52.5 and 64.8 kDa) present only in the P(i)-starved samples. Screening by differential hybridization was performed on a cDNA library constructed from mRNA isolated from P(i)-starved cells. Probes prepared from mRNA from P(i)-deficient and P(i)-sufficient cells identified a number of clones representing mRNA species that were preferentially transcribed under P(i) deficiency. These phosphate starvation-responsive (psr) clones were placed into eleven groups as determined by cross-hybridization. Northern blots showed that the corresponding genes are inducible in both mild and severe P(i) starvation conditions. Preliminary sequencing identified one of the clones as being homologous to beta-glucosidases from several plant species. The possible role of beta-glucosidase during Pi starvation and the identities of the other psr genes are discussed.
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PMID:Isolation of cDNA clones of genes with altered expression levels in phosphate-starved Brassica nigra suspension cells. 764 Mar 58

An inducible intracellular beta-glucosidase (EC 3.2.1.21) from Streptomyces sp. QM-B814 (ATCC 11238) has been purified and characterized. The purified polypeptide is monomeric with a relative molecular mass of 62 kDa by SDS-PAGE and 42 kDa by size-exclusion chromatography; its isoelectric point is 4.2. The difference in the molecular mass values can be attributed to the glycosylated nature of the protein. The purified enzyme has a pH optimum of 6.0-6.5. The temperature optimum for activity is 50 degrees C; at this temperature the enzyme is stable for 1 h. The enzyme hydrolyzes mainly aryl-beta-glucosides but also presents significant activity against beta-linked disaccharides and maltose. The enzyme displays an unusual kinetic behavior and biphasic Lineweaver-Burk and Eadie-Hofstee plots for p-nitrophenyl-beta-D-glucoside and cellobiose were obtained. The enzyme presents beta-glycosyltransferase activity and an exoglycosidase-type action on cellodextrins. It is inhibited by delta-gluconolactone (Ki 0.44 mM) but, remarkably, glucose in the range 25-200 mM enhances the rate of p-nitrophenyl-beta-D-glucoside hydrolysis.
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PMID:Properties of a novel glucose-enhanced beta-glucosidase purified from Streptomyces sp. (ATCC 11238). 766 3

A yeast strain isolated in the laboratory from fermenting agave (Agave sp.) juice was studied and classified as Candida entomophila. The beta-glucosidase of this yeast was purified by ion-exchange chromatography and gel filtration. Its molecular mass estimated by gel filtration was 400 kDa. The oligomeric structure was determined following treatment of the purified enzyme with SDS. Its optimum pH was between 5 and 6, and its optimum temperature was 60 degrees C. The enzyme was active against soluble glucosides with (1-->3)-beta, (1-->4)-beta and (1-->4)-alpha linkage configuration, and it possesses (1-->6)-alpha-arabinofuranosidase activity. It is competitively inhibited by glucose and by D-gluconic acid lactone. The enzyme was constitutive and a glucosyltransferase activity is observed in the presence of ethanol. Since the glycosides present in wines and fruit juices represent a potential source of aromatic flavour, the possible use of the yeast glucosidase for the liberation of the bound aroma is discussed.
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PMID:Purification and characterization of the endocellular beta-glucosidase of a new strain of Candida entomophila isolated from fermenting agave (Agave sp.) juice. 798 78

Phanerochaete chrysosporium is the best studied organism with respect to lignin degradation, but its degradation of the xylan component of lignocellulose is only now being studied. When grown on oat spelt xylan (mainly arabinoxylan), it produces an enzyme with beta-D-xylosidase and beta-D-glucosidase activity. This enzyme was purified by ultrafiltration followed by ammonium sulphate precipitation, anion-exchange chromatography using DEAE Biogel and Mono Q, and gel filtration using Superose 12. It is extracellular, with an apparent M(r) value of 44,500 as determined by SDS-PAGE; the pI is 4.67 and activity is maximal at pH 5 and 60 degrees C. The enzyme is of particular interest because its principal activity is against laminaribiose (3-O-beta-D-glucopyranosyl-D-glucopyranose and laminarin [(1-->3)-beta-D-glucan with ca. 3% of beta-(1-->6) branches] rather than cellobiose and xylobiose. It was competitively inhibited by D-glucono-1,5-lactone and deoxynojirimycin; with p-nitrophenyl beta-D-xylopyranoside as substrate, the Ki values were 32 and 87.5 microM, respectively, and with p-nitrophenyl beta-D-glucopyranoside, they were 35 and 68.7 microM, respectively. The Km values with p-nitrophenyl beta-D-xylopyranoside and p-nitrophenyl beta-D-glucopyranoside as substrates were 3.51 and 5.30 mM, respectively.
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PMID:A Phanerochaete chrysosporium beta-D-glucosidase/beta-D-xylosidase with specificity for (1-->3)-beta-D-glucan linkages. 815 53


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