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:3.2.1.21 (beta-glucosidase)
3,280 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phenotypic characteristics of 100 strains pertaining to the group of mesophilic aeromonas isolated in feces of patients with diarrhea (23 A. hydrophila, 34 A. sobria, 19 A. caviae, and 24 considered atypical because produced a the negative esculin reaction and a positive gas formation from glucose [TSI]). The percentages obtained in the different biochemical tests support the hypothesis that in this group there is a taxonomic complexity. We observed variations in the following tests: LDC, arabinose, Voges-Proskauser, lactose, and motility and hemolytic activity. We compared manual and automatic procedures in detecting esculinase and beta-galactosidase activity (ONPG). The study of constitutional enzymatic activity by means of API ZYM system can not be used to differentiate the distinct species although the enzyme beta-glucosidase is detected preferentially in A. hydrophila.
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PMID:[Phenotypic characteristics of 100 strains belonging to the mesophilic aeromonas group isolated from feces]. 190 54

A cellobiase was purified from the culture supernatant of Neocallimastix frontalis EB188. This enzyme possessed a molecular weight of 85,000 and an isoelectric point of 6.95. The enzyme rapidly hydrolyzed cellobiose, p-nitrophenyl (pNP) beta-D-glucopyranoside (pNPG) and cellotriose and slowly hydrolyzed cellopentaose and salicin. The enzyme did not hydrolyze pNP alpha-D-glucopyranoside or pNP beta-D-cellobioside. Substrate inhibition was observed when cellobiose or pNPG were used as the substrates and glucose production was measured. The kinetic parameters were: K = 0.053 mM, V = 5.88 U/mg of protein and Ki = 0.95 mM for cellobiose; K = 0.36 mM, V = 1.05 U/mg and Ki = 8.86 mM for pNPG. Substrate inhibition was not detected during the hydrolysis of pNPG when pNP production was measured. The kinetic parameters for pNPG were: K = 0.67 mM and V = 1.49 U/mg of protein. The presence of an enzyme.glucose.substrate complex and transglucosylation was evident during the catalysis. Glucose, cellobiose, glucono-delta-lactone, galactose, lactose, maltose and salicin acted as competitive inhibitors during the hydrolysis of pNPG with the apparent inhibition constants (Kis) of 4.8 mM, 0.035 mM, 0.062 mM, 28.5 mM, 0.38 mM, 15.0 mm and 31.0 mM, respectively.
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PMID:Kinetic study of a cellobiase purified from Neocallimastix frontalis EB188. 193 90

Aspergillus niger NCIM 1207 produces high levels of extracellular beta-glucosidase and xylanase activities in submerged fermentation. Among the nitrogen sources, ammonium sulfate, ammonium dihydrogen orthophosphate, and corn-steep liquor were the best for the production of cellulolytic enzymes by A. niger. The optimum pH and temperature for cellulase production were 3.0-5.5 and 28 degrees C, respectively. The cellulase complex of this strain was found to undergo catabolite repression in the presence of high concentrations of glucose. Glycerol at all concentrations caused catabolite repression of cellulase production. The addition of glucose (up to 1% concentration) enhanced the production of cellulolytic enzymes, but a higher concentration of glucose effected the pronounced repression of enzymes. Generally the growth on glucose- or glycerol-containing medium was accompanied by a sudden drop in the pH of the fermentation medium to 2.0.
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PMID:Optimization of cellulase production by Aspergillus niger NCIM 1207. 195 26

Cellobiose transport by the cellulolytic ruminal anaerobe Fibrobacter (Bacteroides) succinogenes was measured using randomly tritiated cellobiose. When assayed at the same concentration (1 mM), total cellobiose uptake was one-fourth to one-third that of total glucose uptake. The abilities of F. succinogenes to transport cellobiose or glucose were not affected by the sugar on which the cells were grown. Aspects of the simultaneous transport of [14C(U)]glucose and [3H(G)]cellobiose, the failure of high concentrations of cold glucose to compete with hypothetical [3H(G)]glucose (derived externally from [3H(G)]cellobiose), and differential metal-ion stimulation of cellobiose transport indicate a cellobiose permease, rather than cellobiase plus glucose permease, was responsible for cellobiose transport. Glucose (10-fold molar excess) partially inhibited cellobiose transport. This was enhanced by prior incubation of the cells with glucose, suggesting subsequent metabolism of the glucose was responsible for the inhibition. Compounds interfering with electron transport or maintenance of transmembrane ion gradients inhibited cellobiose uptake, indicating that active transport rather than a phosphoenolpyruvate:phosphotransferase system catalyzed cellobiose transport. Na+, but not Li+, stimulated cellobiose transport.
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PMID:Cellobiose uptake by the cellulolytic ruminal anaerobe Fibrobacter (Bacteroides) succinogenes. 205 20

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.
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PMID:Purification and properties of a beta-glucosidase from Penicillium oxalicum autolysates. 210 21

The cellular location of beta-1,4-glucosidase activity from, as well as the transport of glucose and cellobiose into, cells of Clavispora lusitaniae NRRL Y-5394 and Candida wickerhamii NRRL Y-2563 was investigated. The beta-glucosidase from Cl. lusitaniae appeared to be a soluble cytoplasmic enzyme. This yeast transported both glucose and cellobiose when grown in medium containing cellobiose as the sole carbon source. Glucose, but not cellobiose, uptake was observed for cells grown on glucose. The Ks and Vmax values for cellobiose transport were different when Cl. lusitaniae was cultured either aerobically (0.11 mM, 6.28 nmol.min-1.mg-1) or anaerobically (0.25 mM, 3.88 nmol-1.min-1.mg-1). The Ks and Vmax values for glucose transport (0.23-1.10 mM and 17.2-33.9 nmol.min-1.mg-1) also differed with the various growth conditions. The beta-glucosidase from C. wickerhamii was extracytoplasmically located. This yeast transported glucose, but not cellobiose, under all growth conditions tested. The Ks for glucose uptake was 0.13-0.28 mM when C. wickerhamii was cultured on cellobiose and 0.25-0.30 mM when cultured on glucose. The Vmax values for glucose uptake were greater for cells cultured on cellobiose (35.0-37.9 nmol.min-1.mg-1) than for cells cultured on glucose (15.6-21.4 nmol.min-1.mg-1). Cellobiose did not inhibit glucose uptake in either yeast. Glucose partially inhibited cellobiose transport in C. lusitaniae, but only if the yeast was grown aerobically. In both yeasts, sugar transport was sensitive to carbonyl cyanide p-trifluoromethoxyphenylhydrazone and 1799, but insensitive to valinomycin.
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PMID:Transport of glucose and cellobiose by Candida wickerhamii and Clavispora lusitaniae. 211 84

A transient-kinetic study of beta-glucosidase from soyabean cell walls was performed with the use of a stopped-flow apparatus. The progress curve of the reaction exhibits a 'slow' burst of about 1 s before the steady state is reached. In the time scale investigated this burst may be accounted for by only one exponential, whose time constant varies with the substrate concentration. As this concentration is increased the value of the time constant increases at first, then decreases. Premixing the enzyme with glucose, the last product of the reaction sequence, reverses the 'slow' burst into a 'slow' lag. Taken together, these results are only compatible with a model that involves the existence of a 'slow' conformational transition of the enzyme.
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PMID:Hysteresis of plant cell-wall beta-glucosidase. 211 38

Two beta-glucosidases (I and II) were isolated from Schizophyllum commune, and their physical and chemical properties studied. The two enzymes have very similar sequences, as shown by HPLC analysis of tryptic digests and partial amino acid sequencing. As judged by their circular dichroism spectra, they have almost identical secondary structure. The estimates for alpha-helix, beta-sheet, and other structures were 21%, 40% and 39%, respectively, for beta-glucosidase I and 27%, 32% and 41% for beta-glucosidase II. Their near-ultraviolet spectra were identical. beta-Glucosidase I was more highly glycosylated than beta-glucosidase II, having 2 mol N-acetylglucosamine/mol enzyme 36, mol mannose/mol enzyme and 1.2 mol glucose/mol enzyme vs 1.2, 17 and 3 mol/mol, respectively, in beta-glucosidase II. The native glycosylated form of beta-glucosidase I had a molecular mass of 102 kDa, and that of beta-glucosidase II, 96 kDa. As estimated from sensitivity to N-glycanase, beta-glucosidase II sugars were mainly asparagine linked, but much of the sugar in beta-glucosidase I was not removed by this treatment and was apparently serine or threonine linked. Kinetic analysis showed that both forms had similar Km values (0.3-2.1 mM) for oligosaccharides of 2-6 residues, but the kcat values of beta-glucosidase II were lower by 30-75% than those of beta-glucosidase I. The substrate dependence of kcat/Km indicated that both enzymes had binding sites for three glucose residues. The pH optimum of beta-glucosidase I was higher than that of beta-glucosidase II (5.8 vs 5.1). Both had similar specificities for several (R)-beta-D-glucosides tested. Both enzymes were competitively inhibited by their glucose product, but beta-glucosidase II was consistently less inhibited than beta-glucosidase I. Cellobiase activity was much more markedly inhibited than the activity with higher oligosaccharides, and the result of this, plus the lower hydrolytic rate with cellobiose, resulted in an accumulation of cellobiose as higher oligosaccharides were digested. Glucono-delta-lactone inhibited both enzymes and the hydrolysis of all oligosaccharide substrates similarly (Ki = 4 microM). We conclude that the catalytic site is identical in both enzymes, but subtle structural differences are reflected in a differential activity on the higher oligosaccharides and in the differential effects of the glucose product as an inhibitor. Furthermore, ethanol had a stimulatory effect on beta-glucosidase I but inhibited beta-glucosidase II, which presumably reflects differential effects of ethanol on the conformations of the two species.
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PMID:Kinetics and specificities of two closely related beta-glucosidases secreted by Schizophyllum commune. 211 5

A gene encoding exo-1,4-beta-D-glucosidase, from Ruminococcus albus AR67, was cloned in Escherichia coli, restriction mapped, and shown to be expressed from sequences within the insert that function as a promoter in E. coli. The cloned enzyme was located predominantly in the cytoplasm (40%) and attached to insoluble cell components (48%). After purification to homogeneity, the enzyme (Mr = 64,000, monomeric) was specific for substrates with beta-D-glucopyranosyl configuration and was inactive against alpha-glucosides, lactosides and xylosides. Km values of the enzyme decreased with increasing chain length (G2-G5). Glucose was the major product of hydrolysis from cellodextrins. Preference for longer chain cellodextrins is consistent with exo-1,4-beta-D-glucan glucohydrolase mode of action [E.C. 3.2.1.74].
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PMID:Mode of action and substrate specificity of a purified exo-1,4-beta-D-glucosidase cloned from the cellulolytic bacterium Ruminococcus albus AR67. 211 79

The kinetics of pNPG, pNPX and cellobiose hydrolysis by beta-glucosidase cloned from C. thermocellum into E. coli was studied. The V values for these substrate hydrolysis are 102, 357 and 6.7 mumols/min/mg protein, respectively; Km are 0.44 mM, 50 mM and 100 mM, respectively, sigma-Gluconolactone inhibits the hydrolysis of all substrates according to a competitive mechanism with Ki of 0.032 mM, 6.0 mM and 0.25 mM, respectively. Glucose inhibits the hydrolysis of pNPG and pNPX also via a competitive mechanism with Ki of 10 mM and 37 mM, while cellobiose--via a mixed type mechanism with Ki of 110 mM and 350 mM. The existence of separate adsorption sites for each substrate and of a common catalytic site for pNPG and pNPX hydrolysis is supposed.
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PMID:[Various kinetic properties of beta-glucosidase cloned from Clostridium thermocellum in E. coli]. 211 22


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