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)

The midgut caecal cells from Rhynchosciara americana larvae possess a plasma-membrane-bound beta-D-glucosidase (cellobiase, EC 3.2.1.21), which is recovered (75-95%) in soluble form both after treatment with Triton X-100 and after treatment with papain. The Triton X-100-solubilized beta-D-glucosidase displays Mr106000 and pI 5.4, whereas the papain-released beta-D-glucosidase shows Mr65000 and pI 4.7. Thermal inactivations of the detergent-solubilized and the papain-released forms of beta-D-glucosidase both follow apparent first-order kinetics with similar half-lives. The papain-released beta-D-glucosidase, after being purified by density-gradient centrifugation, hydrolyses beta-D-glucosides, beta-D-galactosides and beta-D-fucosides at the same active site, as inferred from experiments of competition between substrates. The beta-D-glucosidase seems to operate in accordance with rapid-equilibrium kinetics, since the Km (0.61 mM) for the enzyme is constant over a wide range of pH. The hydrolysis of the beta-D-glucosidic bond catalysed by the beta-D-glucosidase occurs without inversion of configuration, delta-gluconolactone is a strong (Ki 0.5 microM) inhibitor of the enzyme and substituents in the substrate aglycone affect the catalytic constant of the reaction. These data support the assumption that the mechanism of the reaction catalysed by the beta-D-glucosidase involves the intermediary formation of a carbonium ion, rather than a glucosyl-enzyme intermediate.
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PMID:Physical and kinetic properties of a plasma-membrane-bound beta-D-glucosidase (cellobiase) from midgut cells of an insect (Rhynchosciara americana larva). 641 80

Glucocerebroside beta-glucosidase (glucocerebrosidase) activity was assayed from cultured fibroblasts of normal individuals, and patients with type 1 (non-neuropathic), type 2 (acute neuropathic), and type 3 (subacute neuropathic) form of Gaucher disease. Residual glucocerebrosidase activity of patients was 8.9 to 17.4% of normal controls, and there was no clear correlation between the level of residual enzyme activity and the different clinical subtypes of the disease. When membrane-bound glucocerebrosidase activity was assayed in the presence of crude brain lipid extracts or purified phosphatidylserine, enzyme from both the normal and type 1 Gaucher fibroblasts was stimulated dramatically (35-60% by crude extracts, 85-90% by phosphatidylserine). This stimulation was not observed with fibroblast glucocerebrosidase of an infantile type 2 and two juvenile type 3 Gaucher patients. The presence of inhibitors of glucocerebrosidase in these type 2 and type 3 Gaucher cells was not detected. Contrary to the mutant enzyme from these Gaucher fibroblasts, glucocerebrosidase from fibroblasts of two adult type 3 Gaucher patients with cerebral involvement was stimulated substantially (72-85%) by phosphatidylserine. When membrane-bound glucocerebrosidase from fibroblasts of the infantile type 2 and juvenile type 3 patients was solubilized with sodium cholate (1% w/v) and delipidated, the phospholipid stimulation of enzyme activity was restored. These findings suggest that considerable clinical and biochemical heterogeneity exists among patients with neuropathic Gaucher disease and that phosphatidylserine activation cannot be used as a reliable indicator in predicting future onset of neurodegeneration in Gaucher patients. The possibility of an aberrant binding of mutant glucocerebrosidase to the lysosomal membrane in juvenile type 3 form of Gaucher disease is discussed.
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PMID:Gaucher disease: the effects of phosphatidylserine on glucocerebrosidase from normal and Gaucher fibroblasts. 643 68

The lipid requirement of membrane-bound rat liver beta-glucosidase was investigated using 4-methylumbelliferyl-beta-D-glucopyranoside as the substrate. The enzyme was solubilized and delipidated by sequential extraction of a crude lysosomal fraction from rat liver lysosomes with sodium cholate and ice-cold butan-1-ol. Neither saturated nor unsaturated phosphatidylcholine activated this enzyme. In contrast, acidic phospholipids like phosphatidylglycerol (PtdGro) and phosphatidylserine (PtdSer) were effective activators. For the PtdGro series, fatty acid composition was important, with the shorter chain or unsaturated fatty acid-containing PtdGro species being the best activators. Heat-stable factor (HSF) from Gaucher spleen by itself (1-2 micrograms) had no effect on enzyme activity. However, the same amount of HSF when combined with 10 micrograms of PtdSer markedly stimulated beta-glucosidase activity. In the presence of HSF, di-9-cis-octadecenoyl-PtdGro (1 microgram) or -PtdSer (5 micrograms) provided maximum protection of beta-glucosidase against heat (60 degrees C) inactivation. In the absence of phospholipids, HSF had no effect on the rate of inactivation of the enzyme by the suicide inhibitor conduritol B epoxide (t0.5, 12 +/- 0.5 min); the maximum rate of inactivation was achieved in the presence of a mixture of PtdGro (2.5-5 micrograms) and HSF (t0.5, 2.8 min). The combination of PtdSer (10 micrograms) and HSF (1.3 micrograms) lowered the Km for 4-methylumbelliferyl-beta-D-glucopyranoside from 24 to 2.7 mM. Inhibition of the enzyme by the glucocerebrosidase substrate analogues N-hexyl-O-glucosylsphingosine and glucosylsphingosine was influenced by the activator substances. The inclusion of PtdSer and HSF in the beta-glucosidase assay medium lowered the Ki of N-hexyl-O-glucosylsphingosine 20-fold. The same combination of activators decreased the I0.5 of the enzyme for glucosylsphingosine from 89.4 to 7.6 microM. A study of log (Vmax./Km) versus pH indicated that the PtdSer-HSF pair creates the active site of beta-glucosidase, making apparent three ionizable groups on the enzyme with pK values in the range 4.5-5.1.
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PMID:Characterization of the phospholipid requirement of a rat liver beta-glucosidase. 651 62

Studies have been carried out on the activities and properties of the isozymes of alpha-mannosidase, alpha-glucosidase and beta-glucosidase in granulocytes, monocytes, lymphocytes and platelts from peripheral blood of heatlhy adult donors. The findings reveal the differences in activities as well as a characteristic distribution of the different molecular forms of these lysosomal hydrolases in specific cell types. Therefore, the results obtained with unfractionated total leukocyte smples from different subjects may vary according to the distribution of cell types in the circulation. Granulocytes and monocytes show only the acid alpha-mannosidase activity whereas lymphocytes and platelets show both acid and neutral activities. The specific activity of acid alpha-mannosidase in granulocytes and monocytes is higher than in lymphocytes and platelets. By DEAE-cellulose chromatography, the acid alpha-mannosidase in granulocyte and monocyte extracts elutes as two peaks, but only one peak is seen in lymphocytes. All cell types show both acid and neutral alpha-glucosidase activities. The specific activities of both isozymes are higher in granulocytes and monocytes than in lymphocytes and platelets. Monocytes show a higher acid than neutral activity. All other cell types show a higher neutral activity. Beta-Glucosidase in all cell types is mainly membrane-bound and it can be released by Triton X-100 and sodium taurocholate. Taurocholate also stimulates the beta-glucosidase activity of granulocytes, monocytes and lymphocytes whereas it inhibits the activity of this enzyme in platelets. These results indicate that variations in the total number of leukocytes and in the relative proportion of the various cell types in health and disease may yield inconsistent or unreliable values for enzyme activity in the diagnosis of lysosomal storage disease and in carrier detection.
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PMID:Studies on the activities and properties of lysosomal hydrolases in fractionated populations of human peripheral blood cells. 676 26

beta-Glucosidase activity from normal human cultured fibroblasts was not affected by the presence of up to 0.1% (w/v) (1.86 mM) purified sodium taurocholate. At concentrations greater than 0.1%, there was a gradual decrease in activity. Conversely, beta-glucosidase activity from fibroblasts of three patients with juvenile onset Gaucher's disease was preferentially inhibited by the detergent at concentrations as low as 0.025% (0.46 mM). A 40% decrease in activity was observed at 0.1%. Crude sodium taurocholate was more potent in inhibiting beta-glucosidase activity from both the normal and Gaucher fibroblasts. However, very high background fluorescence and inconsistent results were observed when different batches of the crude taurocholate from the same or different sources were used. Similarly, beta-glucosidase activity from Gaucher splenic tissue homogenates, supernatant fluids (40,000 x g) and residue pellets was preferentially inhibited by purified sodium taurocholate. These findings indicate that the reliability and sensitivity of the enzyme assay for Gaucher's disease can be enhanced by determining beta-glucosidase activity in both the absence and presence of purified sodium taurocholate, particularly when variant cases with relatively high residual enzyme activity are encountered. In contrast to the enzyme from fibroblasts and spleens, beta-glucosidase activity from human placenta was markedly activated (greater than 300%) by the presence of 0.08% (1.49 mM) purified sodium taurocholate or 0.1 mM phosphatidyl serine, suggesting the presence of a predominate form of beta-glucosidase, possibly glucocerebroside beta-glucosidase, which is activated by the detergent. The apparent Michaelis constant (Km) for both the soluble and membrane-bound enzyme from normal fibroblasts was 1.6 +/- 0.1 mM. Kms from a patient with severe juvenile Gaucher's disease and two other patients with milder manifestations were 0.8 +/- 0.2 and 3.3 +/- 0.3 mM, respectively.
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PMID:Gaucher's disease II. Studies on the kinetics of beta-glucosidase and the effects of sodium taurocholate in normal and Gaucher tissues. 676 18

Human leukocytes contain at least two isozymes of 4-methylumbelliferyl-beta-glucosidase acting optimally at pH 4.0 and 4.8; in Gaucher disease, only the former is deficient. Brief exposure of the leukocyte homogenate to pH 4.0 at room temperature results in irreversible inactivation of the pH 4.8 activity, while the activity at pH 4.0 remains unaffected. The more acidic isozyme is stimulated four- to fivefold by 0.2% sodium taurodeoxycholate (TDC) with a shift in the pH optimum to 5.0. The less acidic isozyme is completely suppressed in the presence of this detergent. Both leukocyte isozymes appear to be membrane-bound since gel filtration of Sephadex G-200 produces only one peak of activity located at the void volume, unlike in liver and kidney where a second peak also can be demonstrated. Heat inactivation analysis indicated that in controls, assayed in the absence of detergent, pH 4.0 activity is more thermostable than pH 4.8 activity. However, in Gaucher disease, the residual beta-glucosidase at pH 4.0 is just as thermolabile as the unaffected pH 4.8 activity. Heat inactivation of the enzyme in the presence of TDC resulted in rapid loss of activity, suggesting a direct effect of the bile salt on the configuration of the enzyme decreasing its thermal stability. In the absence of detergent, acid beta-glucosidase shows two K(m)'s, one at 3.2 mM and another at 0.9 mM. In the presence of detergent, only the higher K(m) at 3.3 mM is obtained. In patients with Gaucher disease and in obligate carriers, the K(m) remains essentially unaffected while the V(max) shows the expected deficiency.A reliable and reproducible selective assay technique has been developed for the diagnosis of Gaucher disease homozygotes and obligate heterozygotes and for the carrier screening of individuals at risk for this inherited disorder. The efficacy of this technique has been demonstrated by studying the activity in 42 controls, 26 patients, 32 obligate heterozygotes, and 23 healthy relatives of patients with Gaucher disease.
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PMID:Leukocyte beta-glucosidase in homozygotes and heterozygotes for Gaucher disease. 677 Jun 75

Normal human spleen contains two forms of membrane-bound beta-glucosidase, distinguishable by their thermostability and kinetic properties. The spleen from a patient with adult Gaucher's disease was deficient in the major, thermolabile, form of the enzyme.
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PMID:Isoenzymes of membrane-bound beta-glucosidase of human spleen. 677 53

Membrane-bound beta-glucosidase of leukocytes exists in two forms, one with optimal activity at about pH 4.5, whereas the other is most active at pH 5.5-6.0. In one case of type 1 (adult) Gaucher's disease, the pH 4.5 activity was totally deficient, but the pH 5.5 activity was present in normal amounts; obligate heterozygotes had half the normal activity at pH 4.5. In two different cases, the membrane-bound beta-glucosidase was completely absent when assayed at either pH 4.5 or pH 5.5. Two further cases had residual activity at both ph values; however, the residual enzymes had different thermostability properties than the corresponding enzymes of control leukocytes. The results are consistent with the existence of at least three genetic variants of type 1 (adult) Gaucher's disease.
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PMID:Genetic heterogeneity of membrane-bound beta-glucosidase in Gaucher's disease. 678 17

Two forms of membrane-bound beta-glucosidase in the spleen of normal individuals were distinguished by their thermostability properties. The heat-labile form A predominates; it catalyzes the hydrolysis of the natural substrate, glucosylceramide, and is activated by the detergent, sodium taurocholate. The minor heat-stable form B is inactive against glucosylceramide and is inhibited by taurocholate. The activity of form A increases from childhood to adult life, as does the activity of the soluble beta-glucosidase and of glucosylceramide beta-glucosidase. In the spleen of nine patients with different types of Gaucher's disease the residual membrane-bound beta-glucosidase was predominantly heat-stable and inhibited by taurocholate. There was no clear correlation between the properties of the residual enzyme in the different types of the disorder and their respective clinical severity. The results are discussed in relation to the biochemical pathogenesis and the enzymatic diagnosis of Gaucher's disease.
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PMID:Multiple forms of membrane-bound beta-glucosidase in Gaucher's disease. 679 11

Glucosidase activities capable of removing the three glucose residues from Glc3Man9GlcNAc2 oligosaccharide were detected in a cell-free preparation of Saccharomyces cerevisiae X-2180. The glucosidase which cleaves the glucose residue at the nonreducing terminus (Glc3Man9GlcNAc2 oligosaccharide glucosidase) was equally distributed between the particulate and the supernatant fractions obtained after centrifugation of the yeast homogenate at 27,000 X g for 30 min. The membrane-bound activity was stimulated by Triton X-100, whereas the supernatant activity was not affected. The soluble Glc3Man9GlcNAc2 oligosaccharide glucosidase was partially purified from the supernatant by ammonium sulfate fractionation followed by DEAE-Sephadex chromatography. It was clearly separated from alpha-glucosidase, which acts onp-nitrophenyl-alpha-D-glucopyranoside, but still contained beta-glucosidase and alpha-mannosidase acting on p-nitrophenyl-beta-D-glucopyranoside and alpha-D-mannopyranoside, respectively. The Glc3Man9GlcNAc2 oligosaccharide glucosidase had a pH optimum of 6.8, and showed no requirement for divalent cations. The enzyme was very active with glucose-labeled Glc3Man9GlcNAc2, was slightly active with Glc2Man9GlcNAc2, and showed no activity with Glc1Man9GlcNAc2. These properties suggest that this enzyme is involved in the first step of processing of oligosaccharides after transfer from dolichyl pyrophosphate to proteins.
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PMID:Partial purification from Saccharomyces cerevisiae of a soluble glucosidase which removes the terminal glucose from the oligosaccharide Glc3Man9GlcNAc2. 701 69


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