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:2.7.7.8 (polynucleotide phosphorylase)
723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hypophysectomy in rats is accompanied by a significant rise in PNPase activity in ribosomal fractions of the liver. Injection of growth hormone into operated animals produces inhibition of PNPase activity. The linear dependence "dose-response" was recorded with the use of a dosage range of 5 to 100 micrograms/animal. The action of growth hormone was most pronounced 18 hours following its single injection.
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PMID:[Importance of the growth hormone in regulating polynucleotide phosphorylase activity in the rat liver]. 737 Apr 13

Stem-loop structures can protect upstream mRNA from degradation by impeding the processive activities of 3'-5' exoribonucleases. The ability of such structures to impede exonuclease activity in vitro is insufficient to account for the stability they can confer on mRNA in vivo. In this study we identify a factor from Escherichia coli which specifically impedes the processive activity of the 3'-5' exonuclease PNPase at stem-loop structures in vitro. This factor can, potentially, reconcile the apparent discrepancy between the ability of 3' stem-loop structures to stabilize upstream mRNA in vitro and in vivo. Its mechanism of action, and possible role in regulating mRNA degradation, is discussed.
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PMID:mRNA degradation in Escherichia coli: a novel factor which impedes the exoribonucleolytic activity of PNPase at stem-loop structures. 753 70

Remarkable activity of various enzymes involved in adenine nucleotide degradation has been revealed in the endothelium recently. Using the highly sensitive radiochromatographic methods, the activities of 5'-nucleotidase, EC: 3.1.3.5. (5'-Nase), adenine deaminase, EC: 3.5.4.4. (ADase), and purine nucleoside phosphorylase, EC: 2.4.2.5. (PN-Pase) were estimated in the endothelium from normal human aortas characterized by a regular arrangement of cells and in the endothelium from atherosclerotic aortas characterized by different size and often multinucleated cells. Activities of 5'-Nase and ADase in the endothelial cells of atherosclerotic aortas were significantly higher than activities in normal ones. However, the activity of PNPase was approximately on the same level in both aortas. The above findings indicate a shift in the activity of 5'-Nase and ADase, which might be a result of the atherosclerotic process as well as the aggregation of platelets.
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PMID:Activity of some adenine nucleotide degradation enzymes in human atherosclerotic aorta endothelium. 818 97

The platelet population of man and rat can be divided into two classes of about equal size on the basis of presence/absence of an acid phosphatase which acts on para-nitrophenylphosphate (a PNPase), at pH 5. The cytochemical reaction product is in the platelet cytoplasmic matrix, without apparent association with organelles or membrane systems. We could not relate differences in staining to differences in function: all cells responded the same to activation by thrombin, ADP, or collagen, in fibrinogen binding to activated platelets, by endocytosis of fluid-phase tracers, and in internalization of latex particles. With respect to possible physiological substrates for the PNP-ase, there was no reaction product from beta-glycerophosphate, AMP, ADP, ATP, GTP, CMP, IMP, cAMP, creatine phosphate, and inositol phosphates, and the enzyme was not inhibited by 40 mM lithium. There was reaction product from tyrosine phosphate suggesting that the physiological substrate for PNP-ase is tyrosine phosphate. In rat bone marrow, megakaryocytes also were of two classes, PNPase positive and PNPase negative, suggesting that different classes of platelets arise from different classes of megakaryocytes.
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PMID:Blood platelet heterogeneity: evidence for two classes of platelets in man and rat. 752 21

In the presence of Mg2+ ions, polynucleotide phosphorylase (PNPase, EC 2.7.7.8) is known to synthesize RNA-like polymers using ribonucleoside-5'-diphosphate (NDP) substrates but to be unable to utilize deoxyribonucleoside substrates. Our experiments show that when MgCl2 is replaced by FeCl3, PNPase becomes able to synthesize deoxyheteropolymers using deoxyribonucleoside-5'-diphosphates (dNDPs). The deoxyheteropolymer formed from the four dNDPs is degraded by pancreatic DNase, but not by RNase, and is readily used as a template by DNA-dependent DNA polymerase. Synthesis of this DNA-like polymer is accomplished de novo without the help of any primer or preexisting template. What is more, dA/dG and dC/dT ratios of polymers synthesized by different bacterial PNPases closely match ratios found in DNA of the bacterial species the enzyme came from.
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PMID:De Novo Synthesis of DNA-Like Molecules by Polynucleotide Phosphorylase In Vitro 866 1

PNPase and RNase II are the key regulatory exonucleases controlling mRNA decay in Escherichia coli. The rnb transcripts were found to proceed through the terminator and PNPase was found to be involved in the 3' to 5' degradation of rnb mRNA. Analysis of these longer 3' termini revealed that they are located in UA-rich regions. Comparison of single and double mutants suggested that PNPase and RNase II could have different roles in the degradation of these unstructured regions. We have shown that RNase II levels can vary over a fivefold range in haploid cells and that its expression depends on PNPase levels. PNPase-deficient strains were found to have a 2-2.5-fold increase in RNase II activity, while PNPase-overproducing strains reduced the rnb message and RNase II levels. Conversely, the amount of PNPase in the rnb deletion strain was approximately twofold higher than that in the wild-type strain. These observations suggest that the two main exonucleases are inter-regulated through a fine tuning mechanism. We discuss the implications of these results with regard to mRNA degradation and cell metabolism.
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PMID:PNPase modulates RNase II expression in Escherichia coli: implications for mRNA decay and cell metabolism. 880 56

GroEL, as conventionally purified, can be incubated with nucleotides to produce high molecular weight material with an absorption maximum at 260 nm. This material is most clearly demonstrated when samples are subjected to gel filtration under conditions where GroEL is monomeric. There is a time-dependent increase in the high molecular weight material that occurs on incubation with ADP or, more slowly, with ATP. This material is generated during incubation, and none is present in the initial samples. Experiments with nucleases, proteases, radiolabeled nucleotides, and chemical cleavage reagents demonstrate that the high molecular weight material is polyadenylic acid whose formation is inhibited by phosphate. These results are consistent with the GroEL samples containing polynucleotide phosphorylase activity. Nondenaturing gels stained with acridine orange, after incubation in ADP, reveal that the activity producing the poly(A) coelectrophoreses with authentic polynucleotide phosphorylase. Conditions that remove the tryptophan-like fluorescence from preparations of GroEL also remove the PNPase activity. Thus, this activity is not associated with GroEL itself. The results are consistent with reports that GroEL can associate with RNase E and with other studies showing that RNase E and PNPase can form complexes. Thus, the present experiments support suggestions that GroEL can participate in multiprotein complexes that are involved in mRNA processing and degradation.
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PMID:Nucleotides reveal polynucleotide phosphorylase activity from conventionally purified GroEL. 881 Feb 58

Escherichia coli JA300 as the strain catalyzing transglycosylation of nucleic acids has so strong activity. We scrutinized where the high faculty of this strain come from. Using PCR methods with our primer pair MI-1 (up; GTT GAA TTC GCC TTT GTT ATG TCA C) and MI-2 (down; GTT CCG CTA ACG GAA CAC CTA GGC CT), we isolated deoD (the coding region of PNPase) of JA300. Nucleotide sequence analysis indicated that deoD of JA300 is definitely same as that of parent strain K12. The fact that the transcription of deoD of JA300 is more active than that of K12 was also revealed after the analysis by Northrn blot hybridization. These data may suggest that the varieties of gene concerning regulation contribute to the difference of PNPase activity between them.
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PMID:Study of JA300 as agent having high transglycosylation activity. 884 74

The degradation process of the rpsO mRNA is one of the best characterised in E coli. Two independent degradation pathways have been identified. The first one is initiated by an RNase E endonucleolytic cleavage which allows access to the transcript by polynucleotide phosphorylase and RNase II. Cleavage by RNase E gives rise to an rpsO message lacking the stabilising hairpin of the primary transcript; this truncated mRNA is then degraded exonucleolytically from its 3' terminus. This pathway might be coupled to the translation of the message. The second pathway allows degradation of polyadenylated rpsO mRNA independently of RNase II, PNPase and RNase E. The ribonucleases responsible for degradation of poly(A) mRNAs under these conditions are not known. Poly(A) tails have been proposed to facilitate the degradation of structured RNA by polynucleotide phosphorylase. In contrast, we believe that removal of poly(A) by RNase II stabilises the rpsO mRNA harbouring a 3' hairpin. In addition to these two pathways, we have identified endonucleolytic cleavages which occur only in strains deficient for both RNase E and RNase III suggesting that these two endonucleases protect the 5' leader of the mRNA from the attack of unidentified ribonuclease(s). Looping of the rpsO mRNA might explain how RNase E bound at the 5' end can cleave at a site located just upstream the hairpin of the transcription terminator.
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PMID:Multiple degradation pathways of the rpsO mRNA of Escherichia coli. RNase E interacts with the 5' and 3' extremities of the primary transcript. 891 31

Messenger RNA decay in Escherichia coli is slowed in pnp-7 (PNPase) rnb-500 (RNase II) rne-1(RNase E) multiple mutants. We have used Northern blots, S1 nuclease protection and primer extension analysis to map 18 endonucleolytic cleavage sites within the pyrF-orfF dicistronic transcript. Although examination of a total of 27 cleavage sites including those determined for the monocistronic trxA transcript revealed a complex pattern, the central four nucleotides within a cluster of 12 residues encompassing the cleavage sites showed a definite A/U preference. Also of interest was the processing of the dicistronic transcript to remove the downstream orfF sequence as a stable but untranslated RNA fragment. The data provide further support for the hypothesis that multiple decay pathways are involved in the decay of a single transcript. In particular, the pyrF-orfF transcript apparently can be degraded either in the 5' to 3' or the 3' to 5' direction. Our results are discussed in light of current models of mRNA decay involving polyadenylation and multiprotein decay complexes.
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PMID:Analysis of the in vivo decay of the Escherichia coli dicistronic pyrF-orfF transcript: evidence for multiple degradation pathways. 915 69


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