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)

Electron microscope autoradiographic and biochemical methods were used to study the intracellular fates of several 125I-glycoproteins, known to be specifically bound and internalized by the different cell types in the liver. At the earliest times examined (1--2 min), 125I-glycoproteins (ASGP) were localized predominantly along the sinusoidal front of hepatocytes. Analysis of the distribution of autoradiographic grains indicated that: (a) approximately 40--60% of the 125I-ligand could be ascribed to the plasmalemma; (b) a significant fraction had already been internalized; yet (c) very little 125I-ligand was present in the lysosome-Golgi region. Between 4 and 15 min after administration of 125I-ASGPs, there was a dramatic redistribution of autoradiographic grains from regions of the plasmalemma and peripheral cytoplasm (30% decrease) to the lysosome-Golgi region (30% increase). At longer times (30 min), there was continued drainage of 125I-ASGP into this region. The grain density over secondary lysosomes was 60--90 times higher than that over recognizable Golgi elements, clearly indicating that lysosomes were the ultimate destination of the 125I-ASGP. However, no more than 60% of the total 125I-ligand could be localized to lysosome-rich regions of the hepatocyte, with the remaining 40% primarily in the intermediate cytoplasm. Biochemical evidence for proteolysis of the internalized 125I-ASGP (presumably within lysosomes) was obtained when [125I]-mono-iodotyrosine was found in the liver (i.e., hepatocytes) at times later than 15 min. The temporal redistribution observed for mannose and N-acetylglucosamine-terminated glycoproteins (ahexosamino-orosomucoid and agalacto-orosomucoid, respectively) in endothelial cells indicated that the 125I-ligands resided in macropinocytic vesicles (1--15 min) before their ultimate residence in dense bodies (15 min). The same 125I-ligands were also localized to structures resembling secondary lysosomes in Kupffer cells. The lysosomal nature of "these organelles" was implied from the appearance of [125I]mono-iodotyrosine in the liver at later times. 125I-beta-glucuronidase followed the same intracellular pathway in both cell types but was not degraded.
...
PMID:An electron microscope autoradiographic study of the carbohydrate recognition systems in rat liver. II. Intracellular fates of the 125I-ligands. 51 42

1. The total content of neutral sugars in skin of the weanling albino rats kept on the protein-deficient diet was increased by about 40%; this was mainly due to the increased concentration of galactose. The content of sialic acid was increased by about 20%. The collagen nitrogen was decreased significantly, with a concomitant increase of non-collagen nitrogen. At the same time, the content of sulphated glycosaminoglycans in skin was significantly decreased and that of non-sulphated glycosaminoglycans was increased. 2. Protein-deficient diet enhanced the activities of the protein-bound carbohydrate-degrading lysosomal hydrolases, viz. cathepsin D (EC 3.4.4.23), N-acetyl-beta-D-glucosaminidase (EC 3.2.1.30) and beta-D-glucuronidase (EC 3.2.1.31) both in liver and skin. The activity of liver hyaluronidase (EC 3.2.1.35) was also increased upon limitation of protein supply. 3. The changes observed in skin were accompanied by increased concentration of the protein-bound hexoses, hexosamines and sialic acids in serum, and of hexosamine and uronic acid in urine. The serum fucose remained unchanged.
...
PMID:Effect of protein deficiency on the metabolism of glycoproteins and glycosaminoglycans in albino rat skin. 54 53

Adsorptive endocytosis of five different lysosomal enzymes from various human and non-human sources was susceptible to inhibition by mannose and l-fucose, methyl alpha-d-mannoside, alpha-anomeric p-nitrophenyl glycosides of mannose and l-fucose, mannose 6-phosphate and fructose 1-phosphate. A few exceptions from this general scheme were observed for particular enzymes, particularly for beta-glucuronidase from human urine. The inhibition of alpha-N-acetylglucosaminidase endocytosis by mannose, p-nitrophenyl alpha-d-mannoside and mannose 6-phosphate was shown to be competitive. The loss of endocytosis after alkaline phosphatase treatment of lysosomal enzymes supports the hypothesis that the phosphorylated sugars compete with a phosphorylated carbohydrate on the enzymes for binding to the cell-surface receptors [Kaplan, Achord & Sly (1977) Proc. Natl. Acad. Sci. U.S.A.74, 2026-2030]. Endocytosis of ;low-uptake' forms of alpha-N-acetylglucosaminidase and alpha-mannosidase was likewise susceptible to inhibition by sugar phosphates and by alkaline phosphatase treatment, suggesting that ;low-uptake' forms are either contaminated with ;high-uptake' forms or are internalized via the same route as ;high-uptake' forms. The existence of an alternative route for adsorptive endocytosis of lysosomal enzymes is indicated by the unaffected adsorptive endocytosis of rat liver beta-glucuronidase in the presence of phosphorylated sugars and after treatment with alkaline phosphatase.
...
PMID:Evidence for lysosomal enzyme recognition by human fibroblasts via a phosphorylated carbohydrate moiety. 64 6

Glycoproteins having mannose and/or N-acetylglucosamine in the terminal non-reducing position [Stockert, Morell & Scheinberg (1976) Biochem. Biophys. Res. Commun. 68, 988--993], and various lysosomal enzymes [Stahl, Schlesinger, Rodman & Doebber (1976) Nature (London) 264, 86--8] are rapidly cleared from plasma by the liver after intravenous administration. A liver cell-separation technique was used to determine the cellular localization of 125I-labelled beta-glucuronidase, ribonuclease B, agalacto-orosomucoid and asialo-orosomucoid. On a specific readioactivity basis, all ligands except 125I-labelled asialo-orosomucoid were enriched in the non-parenchymal cell fraction. Isolated cells, fixed and stained for beta-glucuronidase or N-acetyl-beta-D-glucosaminidase activity after intravenous injection of the enzymes, showed enrichment in the non-parenchymal cell fraction (probably Kupffer cells). After uptake by the non-parenchymal cells, liver lysosomal beta-glucuronidase and N-acetyl-beta-D-glucosaminidase showed degradation half-times of 2.2 and 0.4 days respectively.
...
PMID:Plasma clearance of glycoproteins with terminal mannose and N-acetylglucosamine by liver non-parenchymal cells. Studies with beta-glucuronidase, N-acetyl-beta-D-glucosaminidase, ribonuclease B and agalacto-orosomucoid. 72 98

1. Structure-linked latency, a trait for most lysosome hydrolase activities, is customarily ascribed to the permeability-barrier function performed by the particle-limiting membrane, which shields enzyme sites from externally added substrates. 2. The influence of various substrate concentrations on the reaction rate has been measured for both free (non-latent) and total (completely unmasked by Triton X-100) hydrolase activities in rat liver cell-free preparations. The substrates were: beta-glycerophosphate, phenolphthalein mono-beta-glucuronide. p-nitrophenyl N-acetyl-beta-D-glucosaminide and p-nitrophenyl beta-D-galactopyranoside. The ratio (free activity/total activity) X 100 is called fractional free activity at any given substrate concentration. 3. The fractional free activity of beta-glucuronidase and beta-N-acetylglucosaminidase were clearly independent of substrate concentration, over the range examined, in both homogenates and lysosome-rich fractions. The fractional free activity of acid phosphatase appeared to be either unaffected (homogenate) or even depressed (lysosome-rich fraction) by increasing the beta-glycerophosphate concentration. The fractional free activity of beta-galactosidase consistently showed a non-linear increase with increasing substrate concentration in both homogenates and lysosome-rich fractions. 4. Procedures such as treatment with digitonin, hypo-osmotic shock and acid autolysis, although effective in causing varying degrees of resolution of the latency of lysosome hydrolase activities, were unable to modify appreciably the pattern of dependence or independence of their fractional free activities on substrate concentration, as compared with that exhibited by control preparations. Ouabain did not affect the free beta-N-acetylglucosaminidase activity of liver homogenates at all. 5. Preincubation of control preparations with beta-glycerophosphate or p-nitrophenyl beta-galactoside did not result in any significant stimulation of the free hydrolytic activity toward these substrates. 6. The results consistently support the view that the membrane of "intact" lysosomes is virtually impermeable to all the substrates tested, except for p-nitrophenyl beta-galactoside, for which the evidence is contradictory. Moreover the progressive unmasking of the hydrolase activities produced by these procedures in vitro reflects the increasing proportion of enzyme sites that are fully accessible to their substrates rather than a graded increase in the permeability of the lysosomal membrane.
...
PMID:Structural equivalents of latency for lysosome hydrolases. 104 Dec 36

A new method for obtaining highly purified hyaluronidase (hyaluronate glycanohydrolase EC 3.2.1.25) in high yield is described. Bull seminal plasma was fractionated with (NH4)2 SO4 and the 30 to 65% saturation fractions were applied to a DEAE-cellulose column. The first protein peak contained hyaluronidase, beta-N-acetylglucosaminidase and beta-glucuronidase. The latter two enzymes were separated by gel filtration on Sephadex G-200. The hyaluronidase was further purified by a Concanavalin-A Sepharose 4B affinity column. By gradient elution with alpha-methyl-D-glucoside a fraction which had a specific activity of 1998 units/mg protein (57 942 National Formulary Standard units/mg protein) was obtained. The highly purified enzyme showed one major protein band on acrylamide gel electrophoresis at pH 4.3. The purified hyaluronidase did not show any beta-glucuronidase or beta-N-acetylglucosaminidase activities. The percent yield of purified hyaluronidase calculated on the basis of total activity was ten times higher than by any pervious method [Yang, C.H. and Srivastava, P.N. (1975) J. Biol. Chem. 250, 79-83].
...
PMID:Purification of bull sperm hyaluronidase by concanavalin-A affinity chromatography. 114 14

The lysosomal form (L form) of beta-glucuronidase was purified 6,500-fold from the liver of C57BL/6J mice with high yield. Purified enzyme was homogeneous as judged by polyacrylamide gel electrophoresis in the presence or absence of sodium dodetcyl sulfate. The microsomal forms of beta-glucuronidase were spontaneously converted to the L form. The purified L form is a tetramer of molecular weight of 280,000 to 300,000, composedd of four identical subunits of 75,000 molecular weight. The enzyme contains a high content of arginine and glutamic acid and a very low content of sulfur-containing amino acids. Approximately 7% of the enzyme molecule is compose of carbohydrate. Sugars in the L form are glucosamine, mannose, galactose, and glucose. Sialic acid and fucose are absent in the enzyme.
...
PMID:Purification and chemical properities of mouse liver lysosomal (L form) beta-glucuronidase. 119 64

In the human adenocarcinoma cell line Caco-2 a substantial amount of a precursor form of the lysosomal enzyme alpha-glucosidase is not segregated into lysosomes, but instead secreted from the apical membrane. In this study we addressed the question whether this process is mediated by mannose 6-phosphate receptors. The subcellular distribution of the cation-independent mannose 6-phosphate receptor was studied by means of electron microscopic immunocytochemistry. The bulk of label was found in the perinuclear region in electron-lucent and dense vesicles, some of the latter bearing a coat. Receptor-containing dense vesicles were also found throughout the cytoplasm. In the apical part of the cells, label for the receptor was present over the surrounding membrane and the interior vesicles of multivesicular bodies, but not over lysosomes. Label on the plasma membrane was mainly restricted to the apical domain. In contrast to alpha-glucosidase, the secreted forms of the lysosomal enzymes cathepsin D, beta-hexosaminidase and beta-glucuronidase are mainly found in the basolateral medium. Enzyme activity measurements and immunoprecipitation of metabolically labeled cells showed that incubation with NH4Cl leads to an enhanced secretion of these enzymes into the basolateral medium, but has no effect on the basolateral secretion of alpha-glucosidase. In addition, NH4Cl caused a minor decrease in the secretion of these enzymes from the apical side and had little or no effect on the secretion of alpha-glucosidase.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:The cation-independent mannose 6-phosphate receptor is not involved in the polarized secretion of lysosomal alpha-glucosidase from Caco-2 cells. 132 37

beta-Glucuronidase from bovine liver was adsorbed to the adsorbents prepared with CH-Sepharose 4B and either the competitive inhibitor or its analogs such as p-aminophenyl 1-thio-beta-D-glucuronic acid, -glucoside, -galactoside, and N-acetyl glucosaminide. The adsorbed enzyme was eluted at 0.1 or 0.5 M NaCl by a stepwise gradient. Chromatography of the enzyme was also performed by using the adsorbents prepared with Epoxy-activated Sepharose 6B and amine compounds or other compounds. In order to see whether the hydroxyl groups of the sugar parts in the ligand are necessary for the adsorption of the enzyme, chromatography was performed by using the adsorbents prepared with sugar derivatives as the ligand. As a result, it was found that beta-glucuronidase had an affinity for adsorbents prepared with either acetyl derivatives or methoxy derivatives of glycosides and CH-Sepharose 4B. From the results of elution of the enzyme with NaCl from adsorbents having amide bonding, it was clarified that the affinity of the enzyme for adsorbents without glycosides in the ligands correlated with acidity of the amide in the adsorbents. Hydrogen bond chromatography was performed with the prepared adsorbents. The enzyme was adsorbed under a high concentration of ammonium sulfate, and the elution of the adsorbed enzyme from adsorbents was examined by the degradation of salt. The enzyme was most easily eluted from aminoethyl 1-thio-beta-D-glucuronic acid-CH Sepharose 4B at 0.9 M ammonium sulfate and at 0.5 M concentration of the salt with p-aminophenyl 1-thio-beta-D-glucuronic acid-CH Sepharose 4B.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Chromatography of beta-glucuronidase from bovine liver. A study of the enzyme binding sites of prepared adsorbents. 139 4

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.
...
PMID:Function and regulation of the murine lymphocyte CD2 receptor. 167 40


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---