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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Centrifugation of the postmitochondrial supernatant of rat liver through 1.0m-sucrose produces particles that have 85-95% less incorporating ability in a cell-free protein-synthesizing system than either ribosomes or microsomes. 2. The incorporation of [(14)C]phenylalanine into protein by particles prepared by sedimentation through 1.0m-sucrose is stimulated about 20-fold by addition of poly U. 3. The content of rapidly labelled RNA of microsomes is decreased during centrifugation through 1.0m-sucrose. 4. It is suggested that degradation of mRNA occurs during the formation of the pellet in the centrifuge tube as a result of a membrane-bound alkaline ribonuclease, after removal of the ribonuclease inhibitor of the soluble fraction.
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PMID:Effect of sedimentation through sucrose solutions on the protein-synthesizing ability of rat liver microsomes. 545 10

1. Free and membrane-bound polyribosomes and ribosomal monomers were isolated from normal and Rauscher-virus-infected mouse spleens by means of discontinuous sucrose density gradients. 2. The addition of ribonuclease inhibitor from rat liver was essential to protect these polyribosomes from degradation. To separate the smooth and rough membranes from ribosomal monomers an additional centrifugation step through a continuous sucrose density gradient was necessary. 3. After infection a marked increase in rRNA from both membrane-bound and free polyribosomes was observed. Treatment of the membrane-bound polyribosomes with sodium deoxycholate yielded only 80S particles even when ribonuclease inhibitor was added. 4. A striking feature of the infected spleen was the occurrence of large polyribosomes. Up to 40 monomers per polyribosome could be counted on electron micrographs.
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PMID:Free and membrane-bound polyribosomes in normal and Rauscher-virus-infected mouse spleen cells. 549 8

Two populations of polyribosomes have been isolated from third instar larvae of D. melanogaster. One population appeared to be soluble while the second seemed membrane-bound. Short-term labeling of the two RNP fractions with radioactive nucleic acid and protein precursors was achieved by using a feeding stimulant. RNA was extracted from both polyribosomal fractions following 25, 40, and 60 min of in vivo uridine-(3)H incorporation. Soluble polyribosomes exhibited more rapid uptake of uridine into ribosomal and heterogeneous RNA fractions than did membrane-bound polyribosomes at comparable time periods. In vivo amino acid incorporation into the two polyribosomal populations was examined after 10, 20, 40, 60, and 80 min of incubation in leucine-(3)H. In this case, the membrane-bound polyribosomes reached a higher specific activity than did the soluble ones. These functional differences confirmed the observation, based on cellular fractionation studies, that the two classes of polyribosomes represented functionally distinct populations. These data have been compared with those from studies on other metazoan systems. In addition, dithiothreitol has been demonstrated to be a powerful ribonuclease inhibitor.
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PMID:Drosophila polyribosomes. The characterization of two populations by cell fractionation and isotopic labeling with nucleic acid and protein precursors. 552 37

Assays of ribonuclease activity in components of mature and immature mammalian erythroid cells indicate that RNase activity is present both in the membrane-free hemolysate and the washed membranes. Erythroid cell RNase exists in an active and latent form. The majority of total cell RNase activity is in the latent state, and is localized to the erythroid cell membrane. Both total and latent RNase activity decline as the cell matures. The latent RNase is released from its relatively firm attachment to the cell membrane and activated by centrifugation or, optimally, by exposure to 4 M urea. The active sites of membrane-associated RNase are apparently oriented toward the inner side of the cell membrane. The properties of the latent membrane-bound RNase which is activated by urea, including K(m), pH optimum, inhibition of enzyme activity by cations, and response to metabolic inhibitors, do not differ significantly from those of the soluble RNase in the membrane-free hemolysate, suggesting that there is only one type of RNase in the erythroid cell. Binding of Rnase to the erythroid cell membrane stabilized the enzyme against inactivation during incubation at 37 degrees C, and the findings suggest that membrane-bound RNase may play a particular part in degrading ribosomes. The findings indicate that the cell membrane has a major role in RNA metabolism in the maturing mammalian erythroid cell.
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PMID:Erythroid cell RNase: activation by urea and localization to the cell membrane. 554 82

1. After incorporation of [(14)C]valine in vitro, cerebral microsomes were separated into membrane-bound and free ribosomes by sucrose-density-gradient centrifugation. 2. In preparations from both 4-day-old and adult rats, free and bound ribosomes incorporated [(14)C]valine. Free ribosomes could be found as polysomes, which were highly active. 3. Microsomes labelled with [(14)C]valine in vitro were fractionated after deoxycholate treatment into a preliminary sediment, sedimented at 105000g (5min.), and ribonucleoprotein particles, sedimented at 150000g (70min.), to determine the role of membrane-bound ribosomes. In the adult the ribonucleoprotein particles retained most of the radioactivity, whereas in the young the preliminary sediment was as highly labelled as the ribonucleoprotein particles. 4. The labelled preliminary sediment from young preparations was both ribonuclease- and deoxycholate-resistant, and the nature of this material is discussed in terms of a possible structural component of microsomal membranes.
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PMID:Microsomal components in relation to amino acid incorporation by preparations from the developing rat brain. 603 14

The intravenous administration of LSD to young adult rabbits resulted in the disaggregation of both free and membrane-bound classes of brain polysomes. Based on the analysis of LSD dosage and the time course of the LSD-induced brain polysome shift, it was found that free polysomes were more sensitive to the drug than the membrane-bound polysome fraction. LSD-induced hyperthermia may be involved in the disaggregation of free and membrane-bound polysomes, since a correlation was found between the extent of LSD-induced hyperthermia and the degree of brain polysome shift. Prevention of LSD-induced hyperthermia by maintaining the animal at 4 degrees C blocked the disaggregation of both polysome classes. Induction of hyperthermia by elevation of ambient temperature also resulted in a shift in free and membrane-bound polysomes. In all cases the disaggregation of polysomes to monosomes was not caused by RNase activation. During polysome disaggregation, polyadenylated mRNA associated with both free and membrane-bound polysomes was not degraded but was relocalized from polysomes to monosomes.
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PMID:Comparison of the effect of intravenous administration of d-lysergic acid diethylamide on free and membrane-bound polysomes in the rabbit brain. 611 Jul 5

Pyrophosphate, p-nitrophenyl phosphate and a variety of pyrimidine and purine nucleotides are hydrolyzed by the solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. The pH optima (or ranges) for hydrolysis of substrates are 8.0 (pyrophosphate), 8.8 (p-nitrophenyl phosphate), 8.4-8.9 (nucleoside monophosphates), and 7.1-8.1 (nucleoside triphosphates); all substrates, with the exception of nucleoside triphosphates, have a higher affinity for the solubilized enzyme at pH 7.4 than at their optimal pH for hydrolysis. ATP is degraded completely by the enzyme preparation to adenosine and inorganic phosphate, but since neither ADP nor ATP accumulate in the incubation medium it is not known whether ATP hydrolysis involves the sequential hydrolysis of terminal phosphate groups. Isoelectric focusing and various chromatographic procedures (gel permeation, ion-exchange and hydrophobic interaction chromatography) fail to separate the alkaline phosphatase, phosphodiesterase, 5'-nucleotidase, adenosine triphosphatase and ribonuclease activities associated with the solubilized membrane preparation. Additionally, inhibitor studies indicate that only a single enzyme with low substrate specificity is involved in the hydrolysis of nucleotides, p-nitrophenyl phosphate, pyrophosphate and hexose phosphate esters. Purines and pyrimidines and their nucleosides interact with the active site, and in some instances activity of the enzyme is stimulated by an unknown mechanism.
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PMID:Nucleotide hydrolysis by solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. 613 88

Young rats were force-fed for 3 days a purified diet devoid of threonine and a number of aspects relating to RNA metabolism in the livers were studied. The findings in the livers of rats force-fed the threonine-devoid diet in comparison with those force-fed the complete diet were as follows: a) poly(A)-mRNA was increased in nuclei and in polyribosomes; b) DNA-dependent RNA polymerases I and II activities were increased; c) in vitro release of 14C-orotic acid labeled RNA from nuclei revealed that transport was unchanged and nucleoside triphosphatase activity of nuclear envelopes was unchanged; d) polyribosomes (total, free and membrane-bound) shifted toward heavier aggregation and in vitro 14C-leucine incorporation into protein was increased; e) RNase activities (at pH 5.4, 7.6, 9.5) were essentially unaltered; and f) in vivo 14C-choline incorporation into microsomal membranes was increased. By administering selected inhibitors of RNA and protein synthesis, such as actinomycin D, alpha-amanitin or cycloheximide, prior to killing the rats force-fed the threonine-devoid or complete diet for 3 days, it was demonstrated that the stimulatory effect on hepatic polyribosomes and protein synthesis in the experimental group was dependent upon new synthesis of poly(A)mRNA and of protein.
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PMID:Studies dealing with hepatic RNA metabolism in rats force-fed a threonine-devoid diet. 616 Feb 24

Poly-[C]-specific ribonuclease (RNase) is released in large amounts from rat pancreas incubated at 37 degrees C in isotonic saline solution. Pancreatic cell disruption by homogenization releases only 10% of that RNase. The remainder, perhaps membrane-bound, is freed only after further membrane deterioration during anoxic incubation. Other tissues (small intestine, stomach, colon, liver, spleen, kidney, muscle, and skin) do not appear to contain much of this RNase or to release it during anoxic incubation. Relatively little amylase is released from the pancreas under the conditions that release RNase. The findings provide a rational basis for monitoring serum RNase levels in patients with acute pancreatitis for early detection and treatment of pancreatic necrosis in man.
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PMID:Release of ribonuclease from anoxic pancreas. 620 Sep 44

Preparations of isolated brush border plasma membrane of Hymenolepis diminuta and H. microstoma possess the following enzymatic activities: alkaline phosphohydrolase (E.C. 3.1.3.1); Type I phosphodiesterase (E.E. 3.1.4.1); ribonuclease (E.C. 3.1.4.22); adenosine triphosphatase (E.C. 3.6.1.3); and 5'-nucleotidase (E.C. 3.1.3.5). The following enzymatic activities could not be demonstrated in either membrane preparation: Type II phosphodiesterase (E.C. 3.1.4.18); cyclic adenosine-3', 5'-monophosphate phosphodiesterase (E.C. 3.1.4.17); leucine aminopeptidase (E.C. 3.4.11.1); maltase (alpha-glucosidase; E.C. 3.2.1.20); and lactase (beta-galactosidase; E.C. 3.2.1.23). These data generally agree with those of previous studies in which similar membrane-bound enzymes were demonstrated in intact (living) worms.
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PMID:A comparison of membrane-bound enzymes of the isolated brush border plasma membranes of the cestodes of Hymenolepis diminuta and H. microstoma. 628 Jan 22


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