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:3.2.1.31 (beta-glucuronidase)
7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Catalytically active mouse beta-glucuronidase (beta-D-glucuronide glucuronosohydrolase, EC 3.2.1.31) is formed when Xenopus oocytes are injected with mouse RNA enriched for poly(A)-containing mRNA sequences. With the RNA from androgen-induced kidneys, the efficiency of translation is comparable to that of endogenous Xenopus messenger, and the fidelity of translation is high. Detection of glucuronidase messenger by formation of a catalytically active product is several orders of magnitude more sensitive than detection by incorporation of isotopically labeled amino acids. As well as providing a sensitive technique for examining the regulation of gene expression, the system makes available an opportunity to study the regulation of post-translational polypeptide processing of a lysosomal enzyme.
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PMID:MRNA-directed synthesis of catalytically active mouse beta-glucuronidase in Xenopus oocytes. 27 Jun 91

Platelets contain a polypeptide growth factor that stimulates the replication of normal connective tissue cells; this platelet-derived growth factor (PDGF) is released during the clotting process. Human platelets from normal volunteers were disrupted by nitrogen cavitation, and the subcellular organelles were fractionated by ultracentrifugation through a 30%--60% sucrose gradient. Electron microscopy revealed that fraction 7 (density 1.23 g/liter) contained the largest number of alpha granules. The specific activity of platelet fibrinogen, an alpha-granule marker, was also highest in this fraction. The subcellular fractions were assay for the presence of PDGF and for beta-thromboglobulin. PDGF was assayed quantitatively by the stimulation of DNA synthesis in confluent growth-arrested BALB/c-3T3 cells, whereas the concentration of beta-thromboglobulin was determined by radioimmunoassay. The highest concentrations of both PDGF and beta-thromboglobulin were found in the alpha-granule fraction. In contrast, beta-glucuronidase, a lysosomal enzyme, was more diffusely distributed and had its highest specific activity in fractions of lower density than those for PDGS, beta-thromboglobulin, or fibrinogen. The data demonstrate that the alpha granules of platelets provide a unique delivery system for PDGF, a polypeptide hormone with growth-promoting activity for connective tissue cells.
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PMID:Platelet alpha granules contain a growth factor for fibroblasts. 44 48

Two polypeptide chains are present in murine beta-glucuronidase precipitated with a specific anti-beta-glucuronidase antibody F(ab)2 fragment. One is the catalytic subunit of beta-glucuronidase and the other has the properties predicted for the hypothetical beta-gluronidase membrane anchor protein. The new protein, named egasyn, is associated with microsomal, but no lysosomal beta-glucuronidase. It is released from the microsomal beta-glucuronidase complex by heat treatment. The YBR strain of mice carrying the Eg degrees mutation does not form an egasyn-beta-glucuronidase complex and is unable to retain beta-glucuronidase on microsomal membranes.
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PMID:Egasyn, a protein complexed with microsomal beta-glucuronidase. 111 92

We used a combination of subcellular fractionation and lactoperoxidase-mediated iodination to examine the polypeptide compositions of three hepatocyte endocytic compartments: early endosomes, late endosomes, and lysosomes. A chemical conjugate of asialoorosomucoid and lactoperoxidase which binds specifically to asialoglycoprotein receptors was perfused through isolated rat livers at 37 degrees C. Subcellular fractions enriched in various endocytic compartments were then isolated by differential and isopycnic centrifugation, and the lactoperoxidase moiety of the internalized conjugate was used to catalyze the iodination of lumenal-facing proteins. The 125I profiles of early and late endosomes were strikingly similar after gel electrophoresis. Using immunoprecipitation, we directly identified and compared the relative amounts of the Na+,K(+)-ATPase and several different acid hydrolases and membrane receptors in all three fractions. The asialoglycoprotein receptor and the low density lipoprotein related protein were approximately nine times more abundant in early endosomes than late endosomes, suggesting that they recycle from early endosomes. In addition, cathepsin D, but not cathepsin L, beta-glucuronidase, and lgp 120, was detected in early endosomes; however, all of these molecules were detected in lysosomes. Our findings provide strong evidence that early endosomes mature into late endosomes and that there is either selective delivery or selective retention of hydrolases at discrete points in the endocytic pathway.
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PMID:Lumenal labeling of rat hepatocyte endocytic compartments. Distribution of several acid hydrolases and membrane receptors. 131 3

The LAC4 gene encoding the beta-galactosidase (beta Gal) of the yeast, Kluyveromyces lactis, was cloned on a 7.2-kb fragment by complementation of a lacZ-deficient Escherichia coli strain. The nucleotide sequence of the structural gene, with 42 bp and 583 bp of the 5'- and 3'-flanking sequences, respectively, was determined. The deduced amino acid (aa) sequence of the K. lactis beta Gal predicts a 1025-aa polypeptide with a calculated M(r) of 117618 and reveals extended sequence homologies with all the published prokaryotic beta Gal sequences. This suggests that the eukaryotic beta Gal is closely related, evolutionarily and structurally, to the prokaryotic beta Gal's. In addition, sequence similarities were observed between the highly conserved N-terminal two-thirds of the beta Gal and the entire length of the beta-glucuronidase (beta Glu) polypeptides, which suggests that beta Glu is clearly related, structurally and evolutionarily, to the N-terminal two-thirds of the beta Gal. The structural analysis of the beta Gal alignment, performed by mean secondary structure prediction, revealed that most of the invariant residues are located in turn or loop structures. The location of the invariant residues is discussed with respect to their accessibility and their possible involvement in the catalytic process.
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PMID:Sequence of the Kluyveromyces lactis beta-galactosidase: comparison with prokaryotic enzymes and secondary structure analysis. 151 85

The CD2 receptor on T-lymphocytes plays a major part in mediating adhesive interactions via the LFA-3 ligand and in transducing signals for lymphocyte activation. In this study the expression, function, and internalization of the CD2 receptor was investigated in resting and activated murine T-cells. Surface iodination of intact lymphocytes showed that both types of cell expressed this antigen as a single polypeptide of 63 KDa, and flow cytometry analysis demonstrated that there was four times as much CD2 on lymphoblasts as on resting cells. Moreover, the CD2 receptor had a more prominent role in the adhesion of the activated lymphocytes to extravascular cells than in the binding of resting cells. Only activated lymphocytes internalized CD2, in the presence or absence of the anti-CD2 monoclonal antibody (mAb) 12-15, more than 80% of the 12-15/CD2 complex being removed from the cell surface within 24 hr. Application of 125I-labelled mAb 12-15 followed by subcellular fractionation on Percoll gradients showed that the complex was internalized initially into a low-density compartment and subsequently transported to heavy-density organelles, in which it was degraded. Immunogold electron microscopy revealed that immediately after the initial binding of mAb 12-15 to the lymphoblasts, the gold particles were localized in clusters exclusively at the plasma membrane. After a short period of culture, the mAb 12-15/CD2 complex was detected in small vesicles near the cell surface. Immunogold staining for a lysosomal enzyme beta-glucuronidase (Gus), for the lysosomal membrane protein LAMP-1, and for the mannose 6-phosphate targetting receptor (MPR) showed that the complex was transported from the endosomal compartment to lysosomal organelles in the activated T-cell. Although mAb 12-15 bound to CD2 in resting T-lymphocytes, in these cells the complex remained associated with the plasma membrane compartment only, even after prolonged culture. These data show that activated but not resting lymphocytes endocytosed the receptor, thereby regulating the expression of this antigen at the plasma membrane. This suggests that the endocytic and lysosomal compartments of lymphocytes have major roles in immune functions, by controlling the level of receptors at the lymphocytes cell surface and thus their response to cytokines and inflammatory mediators as well as their direct interaction with other cells.
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PMID:Function and regulation of the murine lymphocyte CD2 receptor. 167 40

A 1420 bp genomic fragment (lambda-hor1-17) encompassing a Hor-1 gene encoding a C-hordein polypeptide is presented. The deduced amino acid sequence is 261 residues long. It comprises a 20 amino acid signal peptide, unique NH2- and COOH-terminal regions and a coding region comprised of pentapeptide (PQQPY) and octapeptide (PQQPFPQQ) repeat motifs. The 431 bp of 5' non-coding region contains a 'TATA box' at -105, a 'CACA box' (-181 to -201) and a -300 prolamin element. In the 3' non-coding region there are two putative polyadenylation signals located 88 and 142 bp downstream of the stop codon. The structure of lambda-hor1-17 is compared with that of another gene (lambda-hor1-14) encoding a C-hordein polypeptide, which contains an amber codon interrupting the ORF. A functional assay in which the 5' non-coding regions of the two genes were fused to the beta-glucuronidase (GUS) gene demonstrated that both genes were transcriptionally active and that circa 430 bp of the C-hordein promoters were sufficient to drive the expression of the GUS gene in developing barley endosperms. It also demonstrated that both promoters had transcriptional efficiencies comparable with that of the 35S CaMV promoter. The in vitro translation of the coding region of lambda-hor1-14 in the wheat germ system showed that the premature stop codon could be partially suppressed. The suppression was also demonstrated in a transient expression assay in vivo using isolated barley endosperms.
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PMID:Amber codon suppression: the in vivo and in vitro analysis of two C-hordein genes from barley. 193 95

IgE binds to two types of Fc receptors, called Fc epsilon R1 (or high-affinity Fc epsilon R) and Fc epsilon R2 (or low-affinity Fc epsilon R). The Fc epsilon R1 is composed of four polypeptide chains, one alpha, one beta, and two gamma chains. The alpha chain contains the IgE binding site and is a member of the immunoglobulin supergene family. The Fc epsilon R2, also called CD23, consists of one polypeptide chain which shows homology to animal lectin receptors. Fc epsilon R1 are expressed on mast cells and basophils. Crosslinking of the Fc epsilon R1 induces immediate release of mediators of inflammation such as histamine and leukotrienes and delayed secretion of interleukins 4, 5, and 6. Fc epsilon R2 are expressed on resting mu delta + B cells, monocytes/macrophages (M phi), eosinophils, and platelets but rarely on T cells. Interleukin-4 upregulates Fc epsilon R2 expression on B cells and M phi. The functions of Fc epsilon R2 on the different cell types are not fully established and are controversial. Fc epsilon R2 on M phi, eosinophils, and platelets mediate cytotoxicity to schistosomules, enhance phagocytosis, and induce the release of granule enzymes. However, M phi from patients with atopic dermatitis expressing significantly more Fc epsilon R2 than M phi from normals do not release more leukotriene C4, prostaglandin E2, or beta-glucuronidase after incubation with aggregated IgE than normal monocytes. Furthermore, aggregated IgG1 is much more efficient than IgE in inducing mediator release from M phi and IgG1 antibodies are not known to induce immediate-type hypersensitivity reactions. Therefore, definitive proof that Fc epsilon R2 are involved in the pathogenesis of allergic disorders is still lacking. IL-4 appears to play a central role in immediate-type hypersensitivity. It induces human B cells to secrete IgE and IgG4, Ig isotypes typical for antibodies to helminthic parasites and allergens. IL-4 stimulates mast cell growth and upregulates Fc epsilon R2 expression. Interferon-gamma and IL-2 inhibit the IL-4-induced IgG4 and IgE secretion. Whether the abnormally high IgE antibody production in atopic patients is the result of overproduction of IL-4 or deficient IFN-gamma/IL-2 production is presently unknown.
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PMID:Fc receptors for IgE and interleukin-4 induced IgE and IgG4 secretion. 219 Oct 55

S-Adenosylmethionine serves as a methyl group donor in numerous transmethylation reactions and plays a role in the biosynthesis of polyamines and ethylene. We have cloned and sequenced an S-adenosylmethionine synthetase gene (sam-1) of Arabidopsis thaliana. The deduced polypeptide sequence of the enzyme has extensive homology with the corresponding enzymes of Escherichia coli and yeast. Genomic hybridization indicates the presence of two adenosylmethionine synthetase genes per haploid Arabidopsis genome. RNA gel blot analysis shows that adenosylmethionine synthetase mRNA levels are high in stems and roots, correlating well with the higher enzyme activity in stems, compared with leaves. Histochemical analysis of transgenic Arabidopsis plants transformed with a chimeric beta-glucuronidase gene, under the control of 748-base pair 5' sequences of the sam-1 gene, demonstrates that the gene is expressed primarily in vascular tissues. In addition, high expression was observed in sclerenchyma and in the root cortex. A hypothesis for the strong cellular preference in the expression of the sam-1 gene is presented.
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PMID:Strong cellular preference in the expression of a housekeeping gene of Arabidopsis thaliana encoding S-adenosylmethionine synthetase. 253 70

A monoclonal antibody (2C5) raised against rat liver lysosomal membranes was used to identify a 78-kD glycoprotein that is present in the membranes of both endosomes and lysosomes and, therefore, is designated endolyn-78. In cultures of rat hepatoma (Fu5C8) and kidney cells (NRK), this glycoprotein could not be labeled with [35S]methionine or with [32P]inorganic phosphate but was easily labeled with [35S]cysteine and [3H]mannose. Pulse-chase experiments and determinations of endoglycosidase H (endo H) sensitivity showed that endolyn-78 is derived from a precursor of Mr 58-62 kD that is processed to the mature form with a t1/2 of 15-30 min. The protein has a 22-kD polypeptide backbone that is detected after a brief pulse in tunicamycin-treated cells. During a chase in the presence of the drug, this is converted into an O-glycosylated product of 46 kD that despite the absence of N-linked oligosaccharides is effectively transferred to lysosomes. This demonstrates that the delivery of endolyn-78 to this organelle is not mediated by the mannose-6-phosphate receptor (MPR). Immunocytochemical experiments showed that endolyn-78 is present in the limiting membranes and the interior membranous structures of morphologically identifiable secondary lysosomes that contain the lysosomal hydrolase beta-glucuronidase, lack the MPR, and could not be labeled with alpha-2-macroglobulin at 18.5 degrees C, a temperature which prevents appearance of endocytosed markers in lysosomes. Endolyn-78 was present at low levels in the plasma membrane and in peripheral tubular endosomes, but was prominent in morphologically diverse components of the endosomal compartment (vacuolar endosomes and various types of multivesicular bodies) which acquired alpha-2-macroglobulin at 18.5 degrees C, and frequently contained substantial levels of the MPR and variable levels of beta-glucuronidase. On the other hand, the MPR was very rarely found in endolyn-containing structures that were not labeled with alpha-2-macroglobulin at the low temperature. Thus, the process of lysosomal maturation appears to involve the progressive delivery of lysosomal enzymes to various types of endosomes that may have already received some of the lysosomal membrane proteins. Although endolyn-78 would be one of the proteins added early to endosomes, other lysosomal membrane proteins may be added only to multivesicular endosomes that represent very advanced stages of maturation.
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PMID:Endolyn-78, a membrane glycoprotein present in morphologically diverse components of the endosomal and lysosomal compartments: implications for lysosome biogenesis. 265 37


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