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)

Dormant spores of Dictyostelium discoideum contained cellulase at a specific activity of 130 to 140 U/mg of protein; when heat activated, the spores germinated, progressively releasing the cellulase activity into the extracellular medium. The cellulase release was a selective process and resulted in recovery of the cellulase activity at a specific activity of 2,000 U/mg of protein; beta-glucosidase in the spores remained completely associated with the emerging amoebae. Release of the cellulase required heat activation of the spores and occurred during the swelling stage of germination; inhibition of the emergence stage with cycloheximide had no effect on the release of the cellulase. The cellulase activity released consisted of two enzymes whose molecular weights were 136,000 and 69,000. Studies of their pH optima, heat lability, and of their sensitivity to inhibition revealed no distinctive differences between these two proteins. Analysis on diethylaminoethyl-Sephadex columns showed that the higher-molecular-weight protein could be converted into the lower-molecular-weight component in vitro.
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PMID:Cellulases released during the germination of Dictyostelium discoideum spores. 3 62

There are two isozymes of beta-glucosidase in developing cells of Dictyostelium discoideum. A procedure for screening large numbers of clones for beta-glucosidase activity was utilized to obtain mutations which directly affect the activity. We recovered seven strains which lack both isozymes and four strains with residual activity in which enzymatic and physical properties of both isozymes are altered. Beta-Glucosidase appears to act as a block to selfing in macrocyst formation as shown by the fact that ssite mating type to form macrocyst-like structures. Immunological evidence utilizing antisera prepared against purified beta-glucosidase-1 demonstrates that most of the glycosidases in Dictyostelium discoideum share a common antigenic determinant which appears to be added post-translationally. The two isozymes of beta-glucosidase share common protein subunits but the antigenic determinant is either lacking or masked in beta-glucosidase-2. This may account for some of the enzymatic and physical differences between the two isozymes.
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PMID:Structure and function of beta-blucosidases in Dictyostelium discoideum. 5 16

We have studied the effect of a post-translational modification mutation upon four developmentally regulated glycosidases of Dictyostelium discoideum. The presence of the modA mutation affects the intracellular level of these multimeric enzymes differently. The level of alpha-glucosidase is unaffected in the modA mutant. The mutant cell contains only a very small fraction of the wild type beta-glucosidase-1 activity. The alteration in modification renders beta-glucosidase-1 holoenzyme thermolabile and susceptible to degradation in vivo. alpha-Mannosidase-1 and N-acetylglucosaminidase are found at approximately 1/3 of the wild type level in the modA mutant. Degradation of holoenzyme does not appear to be responsible for the low level of these activities. We propose that alpha-mannosidase-1 and N-acetylglucosaminidase subunits are being degraded prior to subunit assembly. We conclude the modification bestows different properties upon the various glycosidases.
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PMID:Effects of a post-translational modification mutation on different developmentally regulated glycosidases in Dictyostelium discoideum. 9 13

The P4 variant of Dictyostelium discoideum is characterized by the production of fruiting structures in which the overall proportion of stalk to spore material is increased, relative to the wild type. The altered morphology of the mutant is due to increased sensitivity to cyclic AMP which promotes stalk cell differentiation. In the presence of 10-4 M-cyclic AMP the entire population of P4 amoebae forms clumps of stalk cells on the surface of the dialysis membrane support. Measurement of changes in activity of a range of developmentally-regulated enzymes during the development of P4 in the presence and absence of cyclic AMP has allowed us to identify three classes of enzyme: (i) Those, such as beta-glucosidase II, trehalose-6-phosphate synthetase and uridine diphosphogalactose-4-epimerase, which are required for the production of spores. (ii) Enzymes, primarily but perhaps not exclusively, required during stalk cell formation. Typical of these are N-acetylglucosaminidase and alkaline phosphatase. (iii) General enzymes, such as threonine dehydrase, alpha-mannosidase and uridine diphosphoglucose pyrophyosphorylase, which are present inboth pre-stalk and pre-spore cells and appear to be necessary for the development of both cell types.
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PMID:Enzyme activity changes during cyclic AMP-induced stalk cell differentiation in P4, a variant of Dictyostelium discoideum. 17 91

The pseudoplasmodium (slug) of the cellular slime mould, Dictyostelium mucoroides consists of prestalk and prespore cells. These 2 differentiated types of cells were separated by modification of the previous methods using density-gradient centrifugation. Major improvements made in the present study were the use of a density column of different specific gravities and the use of a discontinuous gradient rather than a continuous one. With these improvements, it became possible to obtain efficiently a large number of prestalk and prespore cells. After separation of the 2 types of cells, activities and electrophoretic patterns of some developmentally regulated enzymes were compared. The hydrolases such as beta-glucosidase, beta-galactosidase, acetylglucosaminidase and alkaline phosphatase showed higher activities in the prestalk than in the prespore cells. The results are consistent with the fact that more autophagic vacuoles are present in the prestalk than in the prespore cells. On the other hand, UDP-galactose polysaccharide transferase was almost exclusively found in the prespore cells. Electrophoresis on polyacrylamide gels of slug, prestalk and prespore extracts showed that one among 4 isozymes of beta-galactosidase recognized in the slug extract was present only in the prestalk extract. Electrophoretic patterns of acid phosphatase revealed that one of the two isozymes present in the slug was specifically found in the prestalk cell. Finding of such prestalk specific isozymes was significant, since no specific markers have been known for the prestalk cell.
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PMID:Separation and biochemical characterization of the two cell types present in the pseudoplasmodium of Dictyostelium mucoroides. 56 Oct 87

1. The rates of accumulation (enzyme units/h per 10(8) cells) of a number of glycosidase activities were studied in Dictyostelium discoideum cells during the growth and differentiation phases of this organism's life cycle. 2. The rates of accumulation of the enzymes beta-N-acetylglucosaminidase, alpha-glucosidase and beta-galactosidase remain unchanged during the growth and early differentiation phases. 3. The considerable changes in specific activity of the enzymes which occur in the early differentiation phase are due to the massive loss of total cellular protein which occurs at this time. 4. Significant alterations can occur in the rates of accumulation of alpha-mannosidase during both the growth and differentiation phases, and since, on the onset of differentiation, beta-glucosidase activity is excreted and degraded, the rate of accumulation of this enzyme differs in the growth and differentiation phases. 5. The characteristic rates of accumulation of all these glycosidases change markedly with changes in the growth conditions of the myxamoebae, and thus these rates of synthesis must be regulated independently; however, addition of cyclic AMP to the growth medium has no effect on them.
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PMID:Rates of accumulation of glycosidase activities during growth and differentiation of Dictyostelium discoideum. 117 88

Sexual development in Dictyostelium discoideum has many unique features making it an attractive eukaryotic model system for the study of biomembrane fusion and intercellular communication. The work presented here provides primary biochemical evidence for two distinct phases during early sexual development that appear to be defined by calcium-dependent gamete cell fusion. In addition, we introduce a novel procedure for the enrichment of zygote giant cells and use this method to define certain wheat-germ agglutinin binding glycoproteins which are specifically located in zygote giant cells and others which are markers for surrounding amoebae in the second phase of development. In addition, a G protein which is present in high amounts early in development is unique to giant cells in the second phase, suggesting a role in phagocytosis. Finally, alkaline phosphatase activity was found to mark the first phase of sexual development, suggesting a role in cell fusion. This contrasts with the patterns of alpha-mannosidase and beta-glucosidase activity that increase late in the second developmental phase, where they likely function in endocyte digestion during the cytophagic period. The developmental significance of these findings is discussed.
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PMID:Zygote giant cell differentiation in Dictyostelium discoideum: biochemical markers of specific stages of sexual development. 129 42

Although previous studies have indicated that N-linked oligosaccharides on lysosomal enzymes in Dictyostelium discoideum are extensively phosphorylated and sulfated, the role of these modifications in the sorting and function of these enzymes remains to be determined. We have used radiolabel pulse-chase, subcellular fractionation, and immunofluorescence microscopy to analyze the transport, processing, secretion, and sorting of two lysosomal enzymes in a mutant, HL244, which is almost completely defective in sulfation. [3H]Mannose-labeled N-linked oligosaccharides were released from immunoprecipitated alpha-mannosidase and beta-glucosidase of HL244 by digestion with peptide: N-glycosidase. The size, Man9-10GlcNAc2, and processing of the neutral species were similar to that found in the wild type, but the anionic oligosaccharides were less charged than those from the wild-type enzymes. All of the negative charges on the oligosaccharides for HL244 were due to the presence of 1, 2, or 3 phosphodiesters and not to sulfate esters. The rate of proteolytic processing of precursor forms of alpha-mannosidase and beta-glucosidase to mature forms in HL244 was identical to wild type. The precursor polypeptides in the mutant and the wild type were membrane associated until being processed to mature forms; therefore, sulfated sugars are not essential for this association. Furthermore, the rate of transport of alpha-mannosidase and beta-glucosidase from the endoplasmic reticulum to the Golgi complex was normal in the mutant as determined by the rate at which the newly synthesized proteins became resistant to the enzyme, endo-beta-N-acetylglucosaminidase H. There was no increase in the percentage of newly synthesized mutant precursors which escaped sorting and were secreted, and the intracellularly retained lysosomal enzymes were properly localized to lysosomes as determined by fractionation of cell organelles on Percoll gradients and immunofluorescence microscopy. However, the mutant secreted lysosomally localized mature forms of the enzymes at 2-fold lower rates than wild-type cells during both growth and during starvation conditions that stimulate secretion. Furthermore, the mutant was more resistant to the effects of chloroquine treatment which results in the missorting and oversecretion of lysosomal enzymes. Together, these results suggest that sulfation of N-linked oligosaccharides is not essential for the transport, processing, or sorting of lysosomal enzymes in D. discoideum, but these modified oligosaccharides may function in the secretion of mature forms of the enzymes from lysosomes.
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PMID:Sulfated N-linked oligosaccharides affect secretion but are not essential for the transport, proteolytic processing, and sorting of lysosomal enzymes in Dictyostelium discoideum. 211 25

An initial attempt to prepare monoclonal antibodies specific for the Dictyostelium discoideum lysosomal enzyme beta-glucosidase was unsuccessful. All of the antibodies resulting from this fusion recognized an extremely immunogenic epitope that is present on all of the lysosomal enzymes of Dictyostelium. In two succeeding fusions, changes in the immunization schedule intended to increase the immune response to enzyme-specific epitopes were not entirely successful. Although nine hybridomas producing antibodies specific for beta-glucosidase resulted from these two fusions, most (70%) of the cell lines isolated secrete antibodies that recognize the shared, immunodominant epitope. Moreover, the nine beta-glucosidase-specific antibodies proved to be of limited utility since none recognize the native enzyme. Therefore, we attempted to tolerize a BALB/c mouse to the common epitope by injecting the lysosomal enzyme, N-acetylglucosaminidase, within 40 h after birth. As an adult, this animal was immunized with beta-glucosidase. Fusion of the spleen cells from this mouse with myeloma cells resulted in the isolation of nine hybridoma lines that produce antibodies specific for beta-glucosidase. No antibodies reactive with the common epitope were detected. These results suggest that tolerization may provide a means whereby an undesired class of antibody-producing cell lines can be selectively eliminated from the products of a fusion.
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PMID:The use of tolerization in the production of monoclonal antibodies against minor antigenic determinants. 242 54

Radiolabel pulse-chase and subcellular fractionation procedures were used to analyze the transport, proteolytic processing, and sorting of two lysosomal enzymes in Dictyostelium discoideum cells treated with the weak bases ammonium chloride and chloroquine. Dictyostelium lacks detectable cation-independent mannose-6-phosphate receptors and represents an excellent system to investigate alternative mechanisms for lysosomal enzyme targeting. Exposure of growing cells to ammonium chloride, which increased the pH in intracellular vacuoles from 5.4 to 5.8-6.1, slowed but did not prevent the proteolytic processing and correct localization of pulse-radiolabeled precursors to the lysosomal enzymes alpha-mannosidase and beta-glucosidase. Additionally, ammonium chloride did not affect transport of the enzymes to the Golgi complex, as they acquired resistance to the enzyme endoglycosidase H at the same rate as in control cells. When the pH of lysosomal and endosomal organelles was raised to 6.4 with higher concentrations of ammonium chloride, the percentage of secreted (apparently mis-sorted) precursor polypeptides increased slightly, but proteolytic processing of intermediate forms of lysosomal enzymes to mature forms was greatly reduced. The intermediate and mature forms of alpha-mannosidase and beta-glucosidase did, however, accumulate intracellularly in vesicles similar in density to lysosomes. In contrast, in cells exposed to low concentrations of chloroquine the intravacuolar pH increased only slightly (to 5.7); however, enzymes were inefficiently processed and, instead, rapidly secreted as precursor molecules. Experiments involving the addition of chloroquine at various times during the chase of pulse-radiolabeled cells demonstrated that this weak base acted on a distal Golgi or prelysosomal compartment to prevent the normal sorting of lysosomal enzymes. These results suggest that although acidic endosomal/lysosomal compartments may be important for the complete proteolytic processing of lysosomal enzymes in Dictyostelium, low pH is not essential for the proper targeting of precursor polypeptides. Furthermore, certain amines may induce mis-sorting of these enzymes by pH-independent mechanisms.
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PMID:Role of acidic intracellular compartments in the biosynthesis of Dictyostelium lysosomal enzymes. The weak bases ammonium chloride and chloroquine differentially affect proteolytic processing and sorting. 249 37


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