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:3.1.26.9 (ribonuclease)
6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Twenty-two-day-old fetal and five-day-old newborn rats were pretreated with phenobarbital and its hydroxylated metabolites. Drug-metabolizing enzymes (cytochrome P450, epoxide hydrolase, UDP-glucuronosyltransferase, and glutathione-S-transferase) and microsomal ribonuclease were not modified in fetuses treated with 80 or 400 mg . kg-1 of p-hydroxyphenobarbital, in spite of its accumulation in fetal liver. At fetal age, phenobarbital was a poor inducer of drug-metabolizing enzymes. In five-day-old newborns, p-hydroxyphenobarbital provoked a proliferation of endoplasmic reticulum without enzyme induction, whereas phenobarbital induced some drug-metabolizing enzymes. Thus, the effects of p-hydroxyphenobarbital and phenobarbital are retained in five-day-old rats, but undetectable in the fetuses.
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PMID:Comparison of the effects of phenobarbital and its hydroxylated metabolites on drug-metabolizing enzymes during ontogenesis. 681 Feb 95

Glycosylation of N-linked glycoproteins has been stimulated in hen oviduct and bovine pancreas tissue slices by supplementing the tissue culture media with concentrations of dolichylphosphate from 1-100 micrograms/ml. In oviduct, overall incorporation of radioactive sugars into alkali-stable, hot trichloroacetic acid-precipitable material (N-linked glycoproteins) is stimulated approximately 2-fold in dolichylphosphate-supplemented tissues although no stimulation in protein synthesis is observed. Rather, the elevation in glycosylation seems to be a general one involving many protein acceptors. In vitro analysis of microsomal preparations derived from control or dolichylphosphate-supplemented oviduct tissue slices demonstrated a similar enhancement in glycosylation activities that appears to be attributable to an enhanced level of endogenous dolichylphosphate in the microsomes from supplemented tissues. Additionally, when bovine pancreas tissue slices are preincubated with dolichylphosphate and then doubly labeled with [3H]mannose and 14C-labeled amino acids, a 4-fold increase in the ratio of [3H-mannose to 14C-amino acids in secreted ribonuclease is observed relative to the nonsupplemented control. Furthermore, while only 12% of the ribonuclease secreted from control tissue slices specifically binds to concanavalin A-Sepharose, more than 90% of that secreted by dolichylphosphate-supplemented tissue slices binds to the lectin. These data support the notion that dolichylphosphate availability is a limiting factor in the in vivo glycosylation of proteins in these systems.
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PMID:Enhancement of protein glycosylation in tissue slices by dolichylphosphate. 729 17

Hen egg-white lysozyme has been modified by intermolecular cross-linking with dimethyl suberimidate or by acylation with acetic or succinic anhydride. Retention of the native conformation of the modified enzyme was checked by measuring enzyme activity, resistance of disulfide bridges to reduction by thiols, and susceptibility to proteases. Unmodified lysozyme and its derivatives (labelled with 125I) were intravenously injected into nephrectomized rats, and plasma clearance and uptake by liver cells were determined. Under these conditions, about 6% of the unmodified lysozyme was taken up by liver 15 min after injection. Cross-linking led to a greatly increased uptake (up to 89% of the dose in 15 min), whereas acylation reduced the uptake to 3-4%. Cell isolations showed that the unmodified enzyme and the cross-linked derivatives were taken up by sinusoidal cells. Differential fractionation of liver homogenates indicated tht the unmodified enzyme was taken up in lysosomes. The cross-linked derivatives were concentrated in the nuclear and microsomal fractions as well as in the lysosomal fraction, suggesting adsorption on plasma membranes besides uptake in lysosomes. The experiments described in this paper, together with previous results on ribonuclease and lactate dehydrogenase, indicate that endocytosis of some proteins by sinusoidal liver cells is positively correlated with size and positive charge of the molecules.
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PMID:Effect of size and charge on endocytosis of lysozyme derivatives by sinusoidal rat liver cells in vivo. 740 55

The microinjection of cytoplasm taken from one strain of large free-living amoeba into another strain is followed by an incompatibility phenomenon, the inhibition of division amongst the recipient cells. The post-microsomal supernatant fraction from Amoeba discoides (T1D13) injected into A. proteus (T1P) inhibited division in 90% of the injected cells. Further centrifugation of this fraction yielded a pellet which when resuspended and injected, inhibited division in over 95% (and sometimes 100%) of the cells. No inhibitory activity remained in the supernatant after the removal of this pellet. Treatment with 10 micrograms/ml trypsin destroyed the activity of this pellet, while 25 micrograms/ml ribonuclease reduced the inhibitory activity by approximately 40%. Passage of the resuspended post-microsomal pellet through Sephadex G-200 gave one main peak of material which eluted in the void volume. Concentration of this material by either dialysis or lyophilization followed by microinjection into A. proteus showed that this void volume peak contained the inhibitory material, although the most active preparations did not give more than 66% inhibition of division. After elution from Sephadex, the void volume material was analysed by electrophoresis under non-denaturing and denaturing conditions, and by isoelectric focusing. One problem was the loss of inhibitory activity after keeping the pellet at 4 degrees C for 4-5 days, which made further analysis by microinjection difficult. Preliminary experiments using a post-microsomal pellet prepared from Dawson's A. proteus (DP) which inhibited division in A. proteus (T1P) gave a similar profile after Sephadex chromatography and gel electrophoresis.
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PMID:Characterization of a strain-specific inhibitor of cell division from Amoeba cytoplasm. 744 Jun 54

The incorporation of labelled leucine was measured in protein fractions of muscle in intact control and dystrophic female hamsters and also in cell-free preparations obtained from these animals. The labelling of the soluble sarcoplasmic protein fraction, the microsomal protein fraction and the sarcolemma protein fraction was increased in the dystrophic hindleg muscle. The specific radioactivities of the sarcolemma protein fraction and other fractions were increased markedly relative to that of free leucine in the dystrophic muscle. In cell-free preparations where ribonuclease effects were avoided, the dystrophic muscle exhibited an increased synthesis of peptide bonds.
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PMID:Incorporation of amino acids into soluble and membrane protein fractions of dystrophic hamsters. 747 53

The mannose 6-phosphate (Man6P)-dependent pathway for routing lysosomal enzymes was characterized in the hepatopancreas of the estuary crab Chasmagnatus granulata: (a) an acid alpha-L-fucosidase was purified to homogeneity from the above-mentioned organ and was shown to contain mannose-linked phosphate residues; (b) high-mannose-type oligosaccharides isolated from a protein fraction enriched in acid hydrolases were found to contain acid-labile N-acetylglucosamine (GlcNAc) residues; (c) a membrane-bound UDP-GlcNAc:lysosomal enzyme GlcNAc-1-phosphotransferase was detected that phosphorylated the estuary-crab alpha-L-fucosidase and bovine uteroferrin but not bovine pancreas ribonuclease B; (d) a GlcNAc-1-phosphodiester alpha-N-acetylglucosaminidase that released GlcNAc units from GlcNAc alpha 1-P6Man alpha 1-methyl was detected in microsomal membranes of the hepatopancreas; (e) two detergent-solubilized microsomal proteins having molecular masses of 205 and 215 kDa that were retained by a Man6P-rich mannan-Sepharose column, from where they were eluted with Man6P but not with glucose 6-phosphate, were recognized by antisera raised against bovine large (215 kDa) and small (46 kDa) Man6P receptors. This is the first description of all the components of the Man6P-dependent mechanism for routing lysosomal enzymes in an invertebrate.
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PMID:Characterization of the mannose 6-phosphate-dependent pathway of lysosomal enzyme routing in an invertebrate. 765 99

Pure enzyme samples of ribonuclease from Bacillus intermedius 7P (known commercially as 'binase') were investigated for genotoxicity in four microbial tests: the Ames plate incorporation method, AraR-assay; the prophage induction test; and the DNA-repair test. The weak mutagenic effect of binase at high concentrations (0.1 mg/plate, 1 mg/plate) was established by induction of forward AraR-mutations and histidine-reverse mutations (both frameshift mutations and base pair substitution). Metabolic activation with rat or chicken liver, human placenta or plant (from tulip bulbs) microsomal fractions in vitro was seen to abolish the binase mutagenicity. Bacillus intermedius 7P ribonuclease appears to possess DNA damaging activity in uvrA- and polA- mutants, but not in the recA-deficient Escherichia coli strain, and exhibits an induction of recA-dependent mutagenesis detected by the 8-fold increase of the prophage-induction level in lysogenic Bacillus subtilis culture and by the 5-fold increase of this level in the Streptomyces lavendulae 3 lysogenic strain. The importance of the roles of both of enzyme catalytic activity and native structure is emphasized. A proposed mechanism for exogenous ribonuclease action is discussed. Bacillus intermedius 7P ribonuclease probably does not act as a direct genotoxic agent interacting with DNA, but could provoke nucleotide imbalance through its catalytic action on membrane-associated RNAs, which results in alteration of DNA replication and, as a consequence, in recA-dependent mutagenesis.
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PMID:Bacterial ribonuclease: mutagenic effect in microbial test-systems. 766 66

Several studies in the past few years have supported the hypothesis that oxytocin (OT) is synthesized in a paracrine system within the pregnant human uterus and that this paracrine system may be an important regulator of the timing of human parturition. Using ribonuclease protection assays, we have demonstrated a three-fold increase in the rate of synthesis of OT mRNA in human decidua around the time of parturition. We also have shown that a similar increase in OT mRNA and peptide synthesis can be stimulated in vitro by physiological concentrations of estradiol. This increase is inhibited by concomitant use of the estrogen receptor (ER) blocker tamoxifen or by transcription inhibitors. Progesterone had little, if any effect. We also detected mRNAs for ER and progesterone receptor (PR) in amnion, chorion and decidua with the same relative tissue concentrations as OT mRNA. The concentrations of ER but not PR increased significantly around the time of labour onset. To determine if local OT concentrations may be regulated by changes in OT metabolism, we determined kinetic parameters for OT metabolism in decidua, chorion and placenta. [3H]tyrosyl-OT was used as substrate. Metabolites were separated using HPLC and identified using amino acid analysis and mass spectrometry. Metabolism in decidua and chorion occurred predominantly via a cytosolic post-proline endopeptidase and the activity was comparable to placenta. In microsomal fractions, cystine aminopeptidase activity predominated and placenta had significantly more activity than decidua and chorion. There were no changes in any Km or apparent vmax values around the time of parturition. These findings support the existence of a paracrine system within human decidua that involves sex steroids regulating synthesis of OT and that undergoes significant changes around the time of parturition. Changes in local OT concentrations are controlled by rates of synthesis rather than rates of metabolism.
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PMID:Synthesis and metabolism of oxytocin in late gestation in human decidua. 871 92

A 58-kDa protein (ER58) was purified from monkey liver to apparent homogeneity. It accounts for more than 3% of microsomal proteins and is highly conserved among several mammalian species. The amino acid compositions of the N-terminal part and that of two internal peptide fragments present strong similarities with the sequence ascribed to phospholipase C-alpha. Numerous proteins exhibiting a high similarity with this sequence have been isolated by other investigators. Their biological function is controversial. Our purified protein is not active as a phosphatidylinositol-specific phospholipase C, protease or carnitine acyl transferase. Although less efficient than authentic protein-disulfide isomerase, ER58 catalyses the glutathione-dependent reduction of insulin and the reorganization of disulfide bonds of randomly oxidized (scrambled) ribonuclease in reducing conditions. In contrast, ER58 is devoid of oxidizing activity on thiol groups of reduced proteins. Many studies suggest that the proteins bearing the phospholipase C-alpha sequence could be considered as protein-disulfide isomerase isozymes. Our results indicate that ER58 is not totally similar to protein-disulfide isomerase in performing thiol :protein-disulfide oxidoreductase reactions and suggest that the two proteins may exert distinct cellular functions.
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PMID:Purification of a 58-kDa protein (ER58) from monkey liver microsomes and comparison with protein-disulfide isomerase. 966 Feb

Cytochrome P-450 2E1 (CYP2E1) is a readily inducible hemoprotein that catalyzes the oxidation of endogenous compounds and many low molecular weight xenobiotics. As the major component of the microsomal ethanol oxidizing system, it contributes significantly to ethanol metabolism and the formation of the highly reactive metabolite acetaldehyde. The leaky property of this enzyme results in the generation of reactive oxygen species that can induce oxidative stress and cytotoxic conditions deleterious to development. To further investigate the proposed role of CYP2E1 in the etiology of alcohol teratogenesis, the current study focused on the quantification of CYP2E1 in prenatal human brain, a tissue that is highly vulnerable to the damaging effects of ethanol throughout gestation. In microsomal samples prepared from pools of brain tissues, immunoreactive protein was detected by Western blot analysis using enhanced chemiluminescence, whereas functional protein was estimated with an enzymatic assay using p-nitrophenol and an electrochemical detection system. CYP2E1 transcript was consistently detected in RNA samples prepared from individual brain tissues using the ribonuclease protection assay. Quantitative data were collected by scanning densitometry and phosphorimaging technology. There was a dramatic increase in human brain CYP2E1 content around gestational day 50 and a fairly constant level was maintained throughout the early fetal period, until at least day 113. The relatively low levels of the P-450 isoform present in conceptal brain may be sufficient to generate reactive intermediates that elicit neuroembryotoxicity following maternal alcohol consumption.
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PMID:Catalytic activity and quantitation of cytochrome P-450 2E1 in prenatal human brain. 1033 64


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