Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A specific binding site for somatotropin was solubilized by 1% (v/v) Triton X-100 from a crude particulate membrane fraction of pregnant rabbit liver, partially purified and characterized. The solubilized binding site retained many of the characteristics observed in the original particulate fraction, indicating that extraction of the binding site with Triton X-100 does not cause any major changes in its properties. The binding of human 125I-labelled-somatotropin to the solubilized binding site is a saturable and reversible process, depending on temperature, incubation time, pH and ionic environment. Analysis of the kinetic data revealed a finite number of binding sites with an affinity constant of 0.32 x 10(10)M-1. The binding activity for human 125I-labelled-somatotropin was adsorbed to a concanavalin-A-Sepharose column and was dissociated from the column with alpha-methyl-D-glucoside, suggesting that the binding protein may be a glycoprotein. Using affinity chromatography on concanavalin-A-Sepharose, ion-exchange chromatography on DEAE-cellulose and gel filtration on Sepharose 6B, the binding protein was purified 1000-4000-fold from the original liver homogenate. When the partially purified preparation was chromatographed on Sepharose 6B, the binding protein eluted as a molecule with an apparent molecular weight of 200000, with a Stokes' radius of 4.9 nm. Sucrose-density-gradient centrifugation of the preparation showed that the sedimentation coefficient of the binding protein was 7.2S. Isoelectric focusing experiments revealed that a major part of the protein has an acidic pI (4.2-4.5). Exposure of the protein to trypsin decreased the binding activity for human 125I-labelled-somatotropin or bovine 125I-labelled-somatotropin, whereas ribonuclease, deoxyribonuclease, phospholipase C or neuraminidase had little or no effect.
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PMID:Characteristics of solubilized human-somatotropin-binding protein from the liver of pregnant rabbits. 624 70

To gain an understanding of why the polymannose-type oligosaccharide chain of bovine pancreatic ribonuclease B is not processed to a complex-type chain in vivo, the processing of this glycoprotein was studied in two cell-free systems. Addition of native 125I-ribonuclease B to rat liver Golgi membranes in the presence of UDP-GlcNAc resulted in the conversion of the high mannose chain to a complex type as evidenced by the acquisition of resistance to digestion with endoglucosaminidase H. Processing was linearly dependent on time and on the amount of Golgi membranes. Omission of UDP-GlcNAc from the reaction mixtures completely abolished processing of the glycoprotein. Product identification studies confirmed that the formation of ribonuclease that was resistant to digestion with endoglucosaminidase H was accompanied by the appearance of a complex-type oligosaccharide that contained one or more terminal beta-GlcNAc residues. In vitro processing of 125I-ribonuclease B that had been denatured by reduction and alkylation revealed that the rate of complex chain formation was only slightly greater than that observed with the native enzyme. In contrast to the results obtained with the heterologous rat liver system, Golgi membranes from bovine pancreas failed to process native ribonuclease B to the complex form. However, bovine pancreas Golgi membranes did readily process the denatured form of the enzyme. The presence of a factor in bovine pancreas that binds only to native ribonuclease B and thereby prevents its oligosaccharide chain from being processed was considered to be unlikely on the basis of gel filtration studies and mixing experiments. These findings indicate that some aspect of the conformation of native ribonuclease B prevents one or more of the processing enzymes of bovine pancreas from acting on the oligosaccharide chain. In addition, the substrate specificity of this processing enzyme(s) differs markedly from its counterpart in rat liver. These two factors, conformation of the substrate and specificity of the processing enzymes, apparently combine to produce the high mannose oligosaccharide chain of ribonuclease B observed in vivo.
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PMID:Control of asparagine-linked oligosaccharide chain processing: studies on bovine pancreatic ribonuclease B. An in vitro system for the processing of exogenous glycoproteins. 642 84

Even though most of the hepatic binding capacity for mannose-terminated glycoproteins has previously been shown to reside in the hepatocytes (not in the non-parenchymal cells), detailed evidence for the specific uptake of mannose-terminated ligands has been lacking. In the present studies, yeast invertase, a large glycoprotein (Mr 270 000) containing about 50% mannose, was shown to be taken up into hepatocytes by receptor-mediated endocytosis. The uptake was saturable and could be specifically inhibited by mannosides or by a Ca2+ chelator. The asialo-glycoprotein receptor was not involved. The low-Mr (13 000) ligand ribonuclease B, which contains a single high-mannose glycan, was not taken up by hepatocytes; however, it was taken up as fast as invertase by non-parenchymal liver cells. After injection of 131I-invertase into a rat in vivo, about one-half of the labelled protein was recovered in the hepatocytes. On a per-cell basis, each endothelial cell contained 3-4 times as much radioactivity as did the hepatocytes. On fractionation of hepatocytes in sucrose gradients, invertase showed a different intracellular distribution from that of asialo-fetuin, in that invertase moved much faster into that region of the gradient where the lysosomes were recovered. This indicates that invertase and asialo-fetuin are not transported intracellularly by identical mechanisms.
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PMID:Uptake of mannose-terminated glycoproteins in isolated rat liver cells. Evidence for receptor-mediated endocytosis in hepatocytes. 649 38

Oncofetal markers for colon carcinomas are CSAp, a nonsulfated mucin, a second trimester fetal antigen, an altered thymidine kinase, a monosialoganglioside, and glycolipid antigens. For gastric carcinoma, they are basic fetoprotein, a sulfoglycoprotein, and for pancreatic carcinomas--POA, an oncofetal pancreatic antigen, and designated as CAPI, an oncofetal antigen. Tumor-associated markers for colon carcinomas are: UDP-galactosyltransferase and zinc glycinate marker; for gastric carcinomas, sulfated glycoprotein and for pancreatic carcinomas, pancreas carcinoma-associated antigen, a polycytidylic acid-specific ribonuclease, and galactosyltransferase. Suggested as tumor-specific markers for colon carcinomas are an altered mucoprotein, basic antigen, beta 2-microglobulin-associated antigen, and a specific adenosine deaminase; for gastric carcinomas, a specific protein, an antigen with 3-oxyanthranilic acid, and an antigen of unknown origin in gastric secretions; for pancreatic carcinomas, an antigen with molecular weight of 380,000 daltons and an antigen suggested by tumor immunity.
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PMID:Gastrointestinal tumor markers, other than carcinoembryonic antigen, and alpha fetal protein. 688 74

Circulating M antigen, specific for genus Schistosoma, was previously described in serum, urine, patients' milk, and in serum and urine of animals infected by S. mansoni. The M antigen was thermostable and soluble in trichloroacetic acid. It was not hydrolyzed by protease, ribonuclease, amylase, or neuraminidase but destroyed by sodium metaperiodate. In the present study, we have purified the M ag by using trichloroacetic acid solubility, DEAE Sephadex, and immunoadsorption. The M ag showed a neutral electric charge, a m.w. heterogeneity, and was only stained by periodic acid-Schiff. The composition study revealed M ag was a glycoprotein with a polysaccharide moiety (63% of the molecules) particularly rich in galactose, fucose, glucosamine, and mannose, and with a high molecular ratio of serine and threonine. The presence of O-glycosidic linkage allowed M ag to be considered as a mucin or a mucus glycoprotein-like component. It was localized in the cell wall of the gut of adult worms.
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PMID:Purification, immunochemical, and biologic characterization of the Schistosoma circulating M antigen. 698 17

The two major ribonuclease (EC 3.1.27.5) present in normal human urine have been highly purified and extensively characterized for their enzymatic, physical, chemical and structural properties. One of the enzymes, RNAase C, is a glycoprotein which exhibits a pH optimum of 8.5 with RNA as the substrate and preferentially degrades the synthetic homoribopolymer poly(C). This enzyme is resolved into multiple components by column electrofocusing. However, prior treatment with neuraminidase results in a single form of RNAase C with an isoelectric point of 10.4, indicating that the charge heterogeneity is the result of variability in sialic acid content. Amino acid composition and NH2- and COOH-terminal sequence analyses of RNAase C show that this enzyme is very similar to mammalian pancreatic RNAases; the data indicate a peptide chain of 126 amino acid residues and a 33% carbohydrate content. The second enzyme isolated from urine, termed RNAase U, is also a glycoprotein which has a pH optimum of 7.0 with RNA as substrate and is virtually inactive against poly(C). RNAase U lacks sialic acid and focuses as a single component with a highly basic isoelectric point of greater than pH 11.0. The NH2- and COOH-terminal sequences of RNAase U show little homology with the pancreatic RNAases. However, the amino acid composition of this enzyme indicates it is very similar to human spleen RNAase.
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PMID:Purification and properties of ribonucleases from human urine. 721 38

Ribonuclease isolated from human urine is a glucoprotein of molecular weight 33,000. The purified enzyme inhibits: (1) the stimulation of 3H-thymidine uptake into lymphocytes by phytohemagglutinin, pokeweed, and concanavalin A; (2) the growth of pancreatic fibroblastoid cells in in vitro cell culture, and (3) the growth of colonies in bone marrow cell cultures. Ribonuclease levels in the uremic patient vary from 9,500 to 35,000 U/ml (normal 1,041 +/- 247). Serum ribonuclease levels are unaffected by dialytic procedures. It is suggested that the ribonuclease glycoprotein may represent a large number of nondialyzable high molecular weight uremic 'toxins'.
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PMID:Ribonuclease activity in renal failure. Evidence for toxicity. 726 14

Capillary electrophoresis with laser-induced fluorescent detection, a one-dimensional version of the well-established planar analytical method of polyacrylamide gel electrophoresis, has been proven to be a powerful new microanalytical method for profiling complex carbohydrates. In this paper a comparison is presented between the planar high concentration polyacrylamide gel electrophoresis method and capillary electrophoresis of different carbohydrates with respect to performance and efficiency. N-Linked oligosaccharides were released from several glycoproteins, including fetuin, human immunodeficiency virus (HIV) envelope recombinant glycoprotein (GP-120), alpha 1-acid glycoprotein and ribonuclease B, using recombinant peptide-N-glycosidase F (PNGase F). Both separation methods involve labeling of the released carbohydrates at the reducing end with the fluorescent dye, disodium 8-amino-1,3,6-naphthalene trisulfonate (ANTS). Fluorophore labeling was followed by separation of the labeled oligosaccharides either by high concentration polyacrylamide gel electrophoresis or capillary electrophoresis.
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PMID:Capillary and slab gel electrophoresis profiling of oligosaccharides. 749 47

Members of the Rh/T2/S-glycoprotein family of ribonuclease(RNase)-encoding genes have been found predominantly in fungi, plants and bacteria, where they have been implicated in functions as diverse as the phosphate-starvation response and self-incompatibility. We report the isolation and sequence of DmRNase-66B, the first member of this family to be found in an insect genome. This gene was identified by the analysis of a cDNA clone derived from cytological region 66B1-2 of the genome of Drosophila melanogaster. In a search of sequence databases for homologs of this gene, two animal viral proteins, gp53 of the bovine viral diarrhea virus (BVDV) and gp44/48 of the hog cholera virus (HCV), were also found to exhibit the characteristic features of this class of RNases. In all cases, the proteins contain two conserved pentameric amino-acid regions that have been shown to lie in the active site of these RNases. A series of Cys residues are also conserved in all members of this gene family. The discovery of members of this family of genes in an insect genome indicates that these RNases are widely conserved and play important roles in the animal, as well as the plant and prokaryotic kingdoms.
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PMID:The Drosophila melanogaster genome contains a member of the Rh/T2/S-glycoprotein family of ribonuclease-encoding genes. 760 42

Ribonuclease B has become a paradigm as a simple example of an N-linked glycoprotein. We have found that certain affinity-purified preparations of this enzyme demonstrated a pronounced tendency to lose activity if stored as dilute aqueous solutions. Such inactivation is accelerated by the presence of NaCl, but can be counteracted by inclusion of high (1 mol/l) concentrations of xylose. Enzyme activity cannot be restored by addition of xylose after storage of the enzyme. In marked contrast to alpha-methyl-mannoside, xylose does not prevent ribonuclease B from binding to concanavalin A and so may be used to stabilize the enzyme during purification by lectin affinity chromatography.
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PMID:Stabilization of ribonuclease B activity by concentrated xylose solutions. 785


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