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)

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

The mechanism of poly ADPR synthesis and the transfer of poly ADPR to histone H1 molecule by electrophoretically homogenous calf thymus poly ADPR polymerase containing DNA was examined. 1) An acid insoluble radioactive complex (I) was obtained after incubation of purified enzyme with [3H] NAD. The stability of (I) was examined by SDS-polyacrylamide gel electrophoresis. The complex (I) was stable against acid, SDS, urea, DNase and RNase, but labile against pronase, trypsin, alkali and snake venom phosphodiesterase treatment. The molecular weight of (I) was about 130 000 daltons estimated by SDS-gel electrophoresis. The radioactive products of successive alkali, venom phosphodiesterase and Pronase hydrolysis of (I) were PR-AMP and AMP. The mean chain length of poly ADPR of (I) was 20--30. These results suggest that the complex (I) is poly ADP-ribosylated poly ADPR polymerase. 2) Besides (I), a second radioactive peak (II) was observed when acid insoluble products obtained from an incubation mixture containing purified poly ADPR polymerase, [3H] NAD and purified histone H1 were analyzed on SDS-polyacrylamide gel electrophoresis. The molecular weight of (II) was estimated to be about 23 000 daltons. The complex (II) is eluted like histone H1 on CM-cellulose columns and hydrolyzed by alkali, trypsin and snake venom phosphodiesterase but not by DNase, or RNase. The comples (II) was extracted selectively by 5 per cent perchloric acid or 5 per cent trichloroacetic acid from mixture of (I) and (II). The mean chain length of poly ADPR of complex (II) and 5--20; these results suggest that the complex (II) is poly ADP-ribosylated histone H1. 3) Results 1) and 2) indicate that purified DNA containing, thus DNA independent, poly ADPR polymerase catalyzes two different reactions, the ADPR transfer onto the enzyme itself and onto histone H1 and the elongation of ADPR chains. Dimeric forms of ADP-ribosylated histone H1 was not observed. Free poly ADPR was observed only when very small quantities of enzyme were used for incubation.
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PMID:Adenosine diphosphate ribosylation of histone H1 by purified calf thymus polyadenosine diphosphate ribose polymerase. 624 65

Rat peritoneal macrophages contain a chymotrypsin-like protease and its specific inhibitor, both being associated with chromatin of the cells. The inhibitor was separated from the protease by gel filtration through a Sephadex G-75 column, further treated with trypsin, DNase and RNase, and then purified successively on Sephadex G-75, Sephadex G-25, and dihydroxyboryl Bio-Gel P-60 columns. The purified inhibitor had a molecular weight in the range from 2,000 to 3,500 and an absorption maximum at 260 nm at pH 7.0. When the inhibitor was digested by snake venom phosphodiesterase, the inhibitory potency was lost, yielding 5'-AMP and 2'-(5'-phosphoribosyl)-5'-AMP as the digestion products which were identified by high pressure liquid chromatography. The inhibitory potency was neutralized specifically by anti-poly(ADP-ribose) antiserum. The profile of inhibition by the isolated inhibitor was nearly identical with that produced by authentic poly(ADP-ribose). It was therefore concluded that the inhibitor isolated was identical with poly(ADP-ribose), whose chain length ranged from 4 to 7 ADP-ribosyl units. This is the first demonstration that a intracellular protease inhibitor can be endogenous poly(ADP-ribose).
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PMID:Identification of a protease inhibitor from rat peritoneal macrophages as poly(ADP-ribose). 624 11

Microsomal Na, K-ATPase is activated by acetylcholine (5 x 10(-6)--10(-5) M) in a cell-free system including neuronal nuclei and the microsomal--cytoplasmic fraction. No enzyme activation by acetylcholine occurs in the presence of puromycin, actinomycin D and ribonuclease or upon removal of the nuclear or microsomal--cytoplasmic fraction from the system. After preincubation with acetylcholine the membranes reveal a better capacity for phosphorylation by [gamma-32P]ATP and dephosphorylation in the presence of ADP and Na+. The ATP binding by the membranes preincubated in a system with acetylcholine is also increased thereby. It was assumed that acetylcholine induces the synthesis of Na, K-ATPase or its protein activator.
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PMID:[Activation of Na, K-ATPase from nerve cell microsomes by acetylcholine in a model system]. 626 58

The effect of thyrotropin (TSH) on the ADP-ribosylation of endogenous thyroid cell acceptor proteins was examined. Cells were "permeabilized" at 4 degrees C in hypotonic medium and then exposed to [(32)P]- or [(3)H-adenine]NAD(+). The net incorporation of labeled ADP-ribose was measured by trichloroacetic acid precipitation. TSH (100 mU/ml) enhanced ADP-ribosylation with a maximum effect after 30-60 min in the majority of experiments. TSH stimulation was observed even when the incubation contained 1,000-fold more exogenous NAD(+) than the amount of NAD(+) contributed by the permeabilized cells, indicating an effect on enzymatic activity rather than an alteration in NAD(+) pool size or specific activity. No incorporation of radioactivity from labeled NAD(+) was observed in cells not rendered permeable to NAD(+) by hypotonic shock. TSH did not increase the rate of disappearance of trichloroacetic-precipitable radioactivity and did not contain intrinsic NAD(+) glycohydrolase activity. Alkali and snake venom phosphodiesterase, but not ribonuclease or deoxyribonuclease digestion of trichloroacetic acid precipitable thyroid cell radioactivity, revealed primarily 5'-AMP, consistent with an effect of TSH on mono-ADP ribosylation. Nicotinamide and thymidine (50 mM) inhibited both basal and TSH-stimulated ADP-ribosylation of thyroid cell protein. Dibutyryl cyclic (c)AMP (0.1 mM) inhibited endogenous ADP-ribosylation by approximately 35% but had no effect at lower concentrations. 0.5 mM isobutylmethylxanthine inhibited this reaction by approximately 60%. We suggest that TSH enhances thyroid cell ADP-ribosylation by a mechanism independent of cAMP as a second messenger, and that ADP-ribosylation plays a role in the expression of TSH.
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PMID:Hormonal stimulation of eucaryotic cell ADP-ribosylation. 626 5

The substrate specificity of diadenosine 5',5"'-P1,P4-tetraphosphate pyrophosphohydrolase from Physarum polycephalum for dinucleoside polyphosphates has been determined by high-performance liquid chromatography (HP-LC). Elution of a strong anion-exchange resin with a pH and ionic strength gradient of ammonium phosphate separates a series of monoadenosine and diadenosine polyphosphates. Most of the corresponding guanine nucleotides are also resolved on this HPLC system. One mole each of Ap4A and Gp4G is symmetrically hydrolyzed to 2 mol of ADP and GDP, respectively. Ap3A, Ap5A, Ap6A, and Ap4 are hydrolyzed, and in each case ADP is one of the products. Gp3G, Gp5G, Gp6G, and Gp4 are also substrates, and in each case GDP is one of the products. AMP, ADP, ATP, Ap2A, ADPR, GMP, GDP, GTP, NAD+, and NADP+ are not substrates. No hydrolysis of the cap dinucleotides m7Gp3Am and m7Gp3Cm was detected by HPLC. Diadenosine tetraphosphate pyrophosphohydrolase preparations were also assayed for adenylate kinase, nucleotide diphosphate kinase, NAD(P)+ pyrophosphohydrolase, phosphodiesterase, cyclic nucleotide phosphodiesterase, phosphatase, and ribonuclease activities. These enzymic activities were not detectable in diadenosine tetraphosphate pyrophosphohydrolase. The symmetrical hydrolysis of Ap4A and Gp4G is an unique catalytic property that distinguishes diadenosine tetraphosphate pyrophosphohydrolase from P. polycephalum from diadenosine tetraphosphate phosphohydrolases from other organisms.
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PMID:Diadenosine 5',5"'-P1,P4-tetraphosphate pyrophosphohydrolase from Physarum polycephalum. Substrate specificity. 629 57

ADP-ribosyltransferase activity has been characterized in free messenger ribonucleoprotein particles (mRNP) from mouse plasmacytoma cells. This enzymatic activity appears to be associated with the free mRNP and not due to nuclear contamination. The enzyme activity is not stimulated by added DNA or histone H1 and represents 34 per cent of the total cellular ADP-ribosyltransferase activity while the DNA contamination in free mRNP is less than 4 per cent of the total cellular DNA. Moreover, the ADP-ribosyltransferase specific activity per mg of DNA is about 75-fold higher in free mRNP than in the nuclei. During CsCl gradient centrifugation of the cytoplasmic fraction, the ADP-ribosylated material separates out at a buoyant density similar to that of free mRNP. This ADP-ribosyltransferase activity is inhibited by thymidine, nicotinamide and 3-aminobenzamide, while it is highly stimulated by exogenous pancreatic RNase. The in vitro synthesized acid insoluble material is rendered partly soluble by treatment by a proteolytic enzyme or by snake venom phosphodiesterase resulting in phosphoribosyl-AMP formation: the pancreatic RNase does not solubilize this material. Several ADP-ribosylated proteins are detected by lithium dodecylsulfate gel electrophoresis. Such an ADP-ribosyltransferase activity has also been detected in free mRNP from rat liver. It is suggested that this ADP-ribosylation of specific free mRNP proteins may be associated with free mRNP structure and/or with some chemical covalent type of modification rendering mRNA available for translation.
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PMID:Adenosine diphosphate ribosyltransferase and protein acceptors associated with cytoplasmic free messenger ribonucleoprotein particles. 632 87

Poly(ADP-ribose) synthetic activity in isolated nucleoli from rapidly growing mouse ascites tumor cells and ADP-ribosylation of the nucleolar proteins in vitro were studied. The specific activity of the synthesis in the nucleoli was significantly higher than that in the chromatin. The optimum magnesium and NAD+ concentrations, and the effect of RNase treatment on the reaction in the nucleoli were also distinctly different from those in the chromatin. Hydrolysis of the reaction product of the nucleoli with snake venom phosphodiesterase and with calf thymus poly(ADP-ribose) glycohydrolase yielded 5'-AMP and 2'-(5"-phosphoribosyl))5'-AMP, and ADP-ribose, respectively. The average chain length of the polymer formed in the nucleoli was found to be about 4 as a whole, but the distribution was heterogenous, from 1.2 to over 12. Analysis of ADP-ribosylated proteins in the nucleoli by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate revealed that several non-histone proteins with molecular weights of over 100,000 were highly ADP-ribosylated compared with other proteins including histones. This pattern was also different from that of the chromatin. These experimental results demonstrate that the nucleoli are independent from the chromatin as regards poly(ADP-ribose) synthesis in vitro.
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PMID:Poly(ADP-ribose) synthesis in nucleoli and ADP-ribosylation of nucleolar proteins in mouse ascites tumor cells in vitro. 728 63

NAD is normally regarded as a redox molecule or as the substrate for ADP-ribosylation reactions. In this study, we describe the rapid metabolism of NAD by Percoll-gradient-purified lettuce chloroplasts and show that the adenine moiety can be incorporated into RNA in a dark-activated reaction that senses the redox state of the cytochrome b6f complex. Isolated chloroplasts rapidly metabolised radiolabelled NAD+ to 5'-AMP (within seconds) and adenosine during a 60-min incubation in vitro; the products were analysed by high-performance liquid chromatography. No radiolabelled ADP-ribose was detected. Radioactivity was incorporated into trichloroacetic-acid-insoluble material during this period, with approximately 2-4-fold more incorporation occurring in the dark. Most of this radiolabel was rendered acid-soluble by dilute alkaline digestion at 37 degrees C, yielding an approximately equal mixture of 2'-AMP and 3'-AMP, and by RNase digestion, identifying the acid-insoluble radioactive material as RNA. Protein-bound ADP-ribose would have yielded 5'-AMP and/or oligomeric/polymeric ADP-ribose after alkali digestion. The utilisation of NAD metabolites for RNA synthesis was restricted to the thylakoid compartment of the chloroplast. The use of a variety of electron-transport inhibitors such as 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone, bromanil (tetrabromo-1,4-benzoquinone), electron donors (dithiothreitol), electron acceptors (ferricyanide) and an uncoupler showed that the incorporation of radiolabel from NAD into acid-insoluble material was favoured when the cytochrome b6f complex was in the oxidised state (as pertaining to incubations in the dark).
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PMID:NAD turnover and utilisation of metabolites for RNA synthesis in a reaction sensing the redox state of the cytochrome b6f complex in isolated chloroplasts. 750 45

RNAs of Rickettsia prowazekii, an obligate intracytoplasmic bacterium, have been identified and analyzed by an RNase protection assay. Total RNA, a mixture of host cell RNA and rickettsial RNA, was isolated from rickettsia-infected mouse L929 cells by the hot-phenol method. After hybridization with specific antisense RNA probes and digestion with RNase, the protected products were analyzed by electrophoresis and autoradiography. The results show that there is only one mRNA species for the ATP/ADP translocase gene (tlc) but two mRNA species for the citrate synthase gene (gltA). RNA half-lives were determined by measuring the RNA remaining after addition of rifampin. The half-lives of tlc mRNA, gltA mRNA I, and gltA mRNA II in R. prowazekii are 8.4 +/- 0.6, 12.3 +/- 1.3, and 20.5 +/- 1.8 min, respectively. However, the half-lives of tlc mRNA and gltA mRNA I in recombinant Escherichia coli strains are 2.9 +/- 0.1 and 1.4 +/- 0.1 min, respectively. The 16S rRNA in R. prowazekii was also examined and shown to be stable.
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PMID:Identification of tlc and gltA mRNAs and determination of in situ RNA half-life in Rickettsia prowazekii. 769 26


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