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

---

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

A gene encoding a novel cell wall hydroxyproline-rich glycoprotein (HRGPnt3) was isolated from a genomic library of tobacco. The deduced protein (620 amino acids, Mr, 65,406) contains an amino-terminal hydrophobic signal peptide, is highly basic, and is rich in proline, although characteristic Ser-Pro4 repeats are found only beyond residue 204. At the carboxyl terminus, there is a 34-amino-acid unit repeated three times. Arginine is the predominant basic amino acid rather than lysine, as in other HRGPs. A second gene homologous to HRGPnt3 was revealed by Southern blot hybridization of tobacco genomic DNA. Northern blot hybridization identified a 1.9-kb transcript present at low levels in roots. To determine the underlying spatial pattern of expression, the HRGPnt3 promoter and the first 27 nucleotides of the open reading frame were fused to the beta-glucuronidase (GUS) reporter gene and transformed back into tobacco. Histochemical localization of GUS activity showed that the HRGPnt3 promoter was transiently induced in the pericycle and endodermis, specifically in the discrete, small subset of cells involved in the initiation of lateral roots. This pattern of expression, in cells destined to form the tip of the emerging lateral root, indicates that the encoded cell wall protein has a specialized structural function, possibly in the mechanical penetration of the cortex and epidermis of the main root, and that the HRGPnt3 promoter responds to an early morphogenetic signal for lateral root induction.
...
PMID:Specific expression of a novel cell wall hydroxyproline-rich glycoprotein gene in lateral root initiation. 261 9

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.
...
PMID:Endolyn-78, a membrane glycoprotein present in morphologically diverse components of the endosomal and lysosomal compartments: implications for lysosome biogenesis. 265 37

During transit through the epididymis, spermatozoa acquire fertilizing the cell surface exhibits an altered glycoprotein pattern. Epididymal cells and their secretions contribute to these sperm-surface changes. To examine this process, epithelial cells from rat caput and cauda epididymidis were cultured and examined for the synthesis, processing and secretion of two glycoprotein-modifying enzymes, beta-galactosidase and beta-glucuronidase. Cells were cultured four days, incubated with D-2-[3H] mannose and L-[35S] methionine, and placed in isotope-free media. Levels of both cellular and secreted beta-galactosidase and beta-glucuronidase were determined by immunoprecipitation of cell homogenates or medium, followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and scintillation counting of bands. During a 1-h pulse, both caput and cauda cells synthesize two precursor forms of beta-galactosidase (Mr = 84,000 and 87,000), which are processed to the mature (Mr = 63,000) enzyme during a 24-h chase. Caput cells release a high molecular weight (HMW) form (Mr = 90-100,000) and mature beta-galactosidase into the media, but not the Mr = 84-87,000 precursor. On the other hand, cauda cells release mostly mature beta-galactosidase. Ratios of radiolabeled mannose/methionine demonstrate a 7-fold greater mannose content in the cellular precursor of beta-galactosidase than in total protein. Another glycosidase, beta-glucuronidase, is synthesized as a Mr = 78,000-precursor which is processed to the mature Mr = 72,000 form. Medium in which caput and cauda cells were cultured contains both mature enzyme and a Mr = 94,000 form, but no 78,000-precursor form. Ratios of radiolabeled mannose/methionine in the cellular precursor of beta-glucuronidase are 2-fold greater than ratios in the total glycoprotein. Secretion is the major pathway of turnover for several epididymal glycosidases, since more than 50% of the total is secreted/day. These results indicate that cultured epithelial cells from the epididymis synthesize glycosidases and that processing and release differ, depending on the enzyme and the epididymal segment from which the epithelial cells were isolated.
...
PMID:Glycosidases in cultured rat epididymal cells: enzyme activity, synthesis and secretion. 309 Nov 1

Serum amyloid P component (SAP) is a normal human serum protein with pentraxin structure that has morphological and immunochemical identity to the amyloid P component found in normal tissue and amyloid deposits. In the presence of calcium, SAP binds to certain complex polysaccharides, including agarose and zymosan. While the binding of SAP to agarose involves interaction with a galactose pyruvate acetal, the ligand in zymosan has not been defined. In the present study we determined that SAP binds to ligand(s) in a soluble extract of zymosan prepared by alkaline hydrolysis, which contains the mannose oligosaccharide sequences alpha DMan1----3DMan and alpha DMan1----6DMan. SAP did not bind to the alkali-insoluble fraction of zymosan, which is predominantly a glucan polymer, and its binding to zymosan extract which had been absorbed with concanavalin A was markedly reduced, suggesting that mannose residues are involved in the binding of SAP to zymosan. We also demonstrated that SAP binds to the glycoproteins ovalbumin, thyroglobulin, beta-glucuronidase and C3bi, which contain mannose-terminated sequences, while it did not bind to native and desialized preparations of ovomucoid, alpha 1-acid glycoprotein and glycophorin, which lack terminal mannose residues. SAP did not bind to pneumococcal C polysaccharide or to N-acetylglucosamine oligosaccharides covalently linked to a protein carrier. The binding of SAP to ligand(s) in zymosan extract or ovalbumin was inhibited by the preincubation of SAP with either zymosan extract or ovalbumin glycopeptides, both of which share similar mannose oligosaccharide sequences. All of the SAP binding reactions required calcium, were maximal at approximately 1 mM calcium, and gave similar results whether purified SAP or SAP in serum was used. These findings indicate that mannose-terminated oligosaccharides of polysaccharides and glycoproteins represent a new class of ligands for SAP and suggest that SAP may function as a mannose-binding protein.
...
PMID:Evidence that serum amyloid P component binds to mannose-terminated sequences of polysaccharides and glycoproteins. 321 Nov 59

The structure of the basement membrane of the high endothelium of reactive human lymph nodes was investigated by techniques selective for carbohydrates (periodic acid-Schiff; critical electrolyte concentration staining with Alcian Blue; lectin histochemistry), specific proteins (immunohistochemistry for laminin and fibronectin) and by conventional techniques of light and transmission electron microscopy. Adjacent small lymphocytes were assigned to B and T cell subsets by use of monoclonal antibodies and they were analysed for non-specific esterase, beta-glucuronidase, beta-N-acetylglucaminidase and proteolytic activities. The basement membranes were shown to be distinctive and to contain three layers, of differing laminin, glycosaminoglycan and glycoprotein oligosaccharide content. Certain lymphocytes (probably T) contained enzymes potentially able to degrade some components of these basement membranes.
...
PMID:The structure of the basement membrane of human lymph node high endothelial venules: an ultrastructural, histochemical and immunocytochemical study. 353 3

Rabbit alveolar macrophages express a plasma-membrane receptor that recognizes glycoprotein ligands bearing terminal mannose, fucose or N-acetylglucosamine residues. Macrophage membranes were washed extensively with buffers containing high salt and mannose or EDTA to remove endogenously bound ligand, before Triton X-100 extraction. The extracts were chromatographed on mannose-Sepharose. Elution with mannose, followed by dialysis and a second mannose-Sepharose step with EDTA elution, produced a preparation that migrated as single protein band of Mr 175,000 on SDS/polyacrylamide-gel electrophoresis. The purified protein binds mannose-BSA (bovine serum albumin) with a dissociation constant of 1.9 X 10(-8) M. Ligand binding is Ca2+ and pH-dependent, with maximal binding at neutral pH and low binding below pH 6.0. The binding of 125I-mannose-BSA is inhibited by ligands bearing high-mannose oligosaccharides, such as mannan or beta-glucuronidase, as well as the monosaccharides mannose, fucose and N-acetylglucosamine. Galactose, galactosylated BSA, glucose and mannose 6-phosphate are non-inhibitory. Amino acid compositional analyses indicate that the receptor contains high concentrations of aspartate/asparagine and glutamate/glutamine, and low amounts of methionine. The carbohydrate composition was studied by lectin overlays of electrophoretically transferred receptor, and the results indicate the presence of N-linked complex and O-linked sialylated oligosaccharides. A protein of Mr 175,000 was immunoprecipitated from radio-iodinated macrophage membranes with an antibody generated against purified rabbit lung mannose receptor.
...
PMID:Isolation and characterization of a mannose-specific endocytosis receptor from rabbit alveolar macrophages. 366 87

The water-soluble proteins of the rat preputial gland secretion were characterized in native and SDS-treated form on polyacrylamide gel electrophoresis. Nine major proteins were present in the secretion. One protein was a glycoprotein of molecular weight greater than 200,000 with beta-glucuronidase activity, and the other eight proteins had a molecular weight of 17,000, but with different charges. Acid phosphatase and arylsulphatase activities were present in the secretion in minor amounts. The isoelectric points of the secretory proteins ranged from 8.5 to 5.3; none of the proteins were lipoproteins, and there were no sex differences. The male and female rat urinary proteins were also characterized electrophoretically. The male rats had two different protein patterns, probably genetically determined. The female rats showed basically one urinary protein pattern, but their urines were frequently mixed with the preputial gland secretory proteins, which most likely played a part in the chemical communication. The mixing could not be correlated to daytime or estrous cycle.
...
PMID:Characterization of the secretory proteins of rat preputial gland in relation to urinary proteins. 372 92

The glycoprotein egasyn complexes with and stabilizes precursor beta-glucuronidase in microsomes of several mouse organs. Several observations indicate egasyn is, in addition, an esterase. Liver homogenates of egasyn-positive strains have specific electrophoretically separable esterases which are absent in egasyn-negative mice. These esterases react with anti-egasyn serum. A specific esterase was likewise complexed with immunopurified microsomal beta-glucuronidase. The esterases were, like egasyn and microsomal beta-glucuronidase, concentrated in the microsomal subcellular fraction. Egasyn which is not bound to beta-glucuronidase, which represents 80-90% of total liver egasyn, is not complexed with other liver proteins. Egasyn, therefore, specifically stabilizes beta-glucuronidase in microsomes. The esterase activity is inhibited by bis-p-nitrophenyl phosphate indicating it is a carboxyl esterase. Several possible functions of egasyn-esterase activity are discussed.
...
PMID:Egasyn, a protein which determines the subcellular distribution of beta-glucuronidase, has esterase activity. 406 95

1. Rat kidney lysosomal glycoproteins, prelabelled in the N-acetylneuraminic acid and polypeptide portions with N-acetyl[(3)H]mannosamine and [(14)C]lysine, or with N-acetyl-[(14)C]glucosamine, were incubated under various conditions. Autolytic cleavage of labelled N-acetylneuraminic acid and peptide was maximum at pH5.0. 2. N-Acetylneuraminic acid was released more rapidly than peptide during incubation at 37 degrees or 4 degrees C at pH5. p-Nitrophenyloxamic acid, an inhibitor of bacterial neuraminidase (Edmond et al., 1966), inhibited the cleavage of N-acetylneuraminic acid and peptide, and also inhibited cathepsin D activity. 3. Galactono-, mannono-, and glucono-lactone, inhibitors of the corresponding glycosidases, blocked the autolytic cleavage of N-acetyl[(14)C]glucosamine and protein without inhibiting beta-N-acetylhexosaminidase or cathepsin D activity. These findings suggest that the carbohydrate side chains protect the polypeptide portion of the lysosomal glycoproteins against proteolytic attack by lysosomal cathepsins. 4. In electrofocusing experiments, autolysis was minimized by adding 0.1% p-nitrophenyloxamic acid to the media used for extraction and electrofocusing, and by maintaining an alkaline pH (pH8.8-9) during extraction and dialysis. Arylsulphatase occurred in two forms with pI values of 4.4 and 6.4-6.7, and beta-glucuronidase in two forms with pI values of 4.4 and 6.1. When [(14)C]lysine and N-acetyl[(3)H]mannosamine were given to rats 1.5 and 1 h before killing, (14)C and (3)H were largely restricted to highly acidic glycoprotein species with pI values of 2.1-5.1. 5. When a lysosomal extract was adjusted to pH5 and incubated at 20 degrees C for 16h and then at 37 degrees C for 1 h before electrofocusing, 32 and 58% of the labelled peptide and N-acetylneuraminic acid was cleaved and the pI values of the labelled glycoproteins were markedly increased. About 80% of the acidic form of arylsulphatase and beta-glucuronidase was recovered with the basic form, and the pI of the basic form of both enzymes rose to 7.0. Similar, though less marked changes, were observed when a lysosomal extract was kept at pH5 for 2h at 4 degrees C before electrofocusing. 6. When an acidic lysosomal fraction (pI4.2-4.6) was incubated at pH5 for 2.5h and refocused, 80% of the arylsulphatase now occurred in two forms with pI values of 5 and 6.4. When a basic lysosomal fraction (pI5.8-6.4) was similarly incubated, the pI of arylsulphatase increased from 6.4 to 7.2. The relative increase in pI of arylsulphatases was accompanied by a proportional loss of N-acetylneuraminic acid from the glycoprotein associated with these forms. 7. These experiments show that lysosomal glycoproteins and two representative hydrolases, when exposed to a mildly acidic pH, readily undergo autolytic degradation and their pI values increase. These observations may have a bearing on the origin of the molecular heterogeneity of the lysosomal enzymes.
...
PMID:Autolysis of glycoproteins in rat kidney lysosomes in vitro. Effects on the isoelectric focusing behaviour of glycoproteins, arylsulphatase and beta-glucuronidase. 445 20

1. The following fractions were prepared from rat kidney and characterized ultrastructurally, biochemically and enzymically: (a) an ordinary rough microsomal (RM(1)) fraction; (b) a special rough microsomal (RM(2)) fraction enriched seven- to nine-fold in acid hydrolases over the homogenate; (c) a smooth microsomal (SM) fraction; (d) a Golgi (GM) fraction enriched 2.5-fold in acid hydrolases and 10-, 15- and 20-fold in sialyltransferase, N-acetyl-lactosamine synthetase and galactosyltransferase respectively; (e) a lysosomal (L) fraction enriched 15- to 23-fold in acid hydrolases. The frequency of Golgi sacs and tubules seen in the electron microscope and the specific activity of the three glycosyltransferases in these fractions increased in the order: RM(2)<RM(1)<SM<GM. 2. Five lysosomal hydrolases, acid phosphatase, beta-N-acetyl-hexosaminidase, beta-galactosidase, beta-glucuronidase and arylsulphatase, were characterized in these fractions with respect to (a) solubility on freeze-thawing and (b) electrophoretic mobility in polyacrylamide gels. 3. In the RM(2) fraction each of these hydrolases occurred largely or exclusively as a single bound basic form coincident with cationic glycoprotein bands in gels (Goldstone et al., 1973). 4. In the L fraction these hydrolases were present largely as soluble, acidic (anionic) forms. 5. The solubility, electrophoretic heterogeneity and anodic mobility of these hydrolases increased progressively in subcellular fractions in the order: RM(2)<RM(1)<SM<GM<L. 6. These findings, together with evidence cited in the text showing that N-acetylneuraminic acid residues are responsible for the solubility and electronegative charge of these acidic forms and incorporation of these residues into the Golgi apparatus, support the following scheme for the biosynthesis of lysosomal enzymes. Each hydrolase is synthesized as a bound basic glycoprotein enzyme in a restricted portion of the rough endoplasmic reticulum. The soluble, acidic forms are generated as the nascent glycoprotein enzymes migrate through the Golgi apparatus through the attachment of sugar sequences containing N-acetylneuraminic acid.
...
PMID:Physicochemical modifications of lysosomal hydrolases during intracellular transport. 472 40


<< Previous 1 2 3 4 5 6 Next >>

---