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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)

The kinetic model of carbohydrate metabolism has been expanded to include: (a) the accumulation of alpha and beta-cellulose, insoluble cell-wall glycogen and mucopolysaccharide; (b) the role of RNA turnover as a source of carbon for end-product synthesis and as a buffer regulating the level of uridine nucleotides in this metabolic network; and (c) the role of purine-nucleoside phosphorylase, 5'-AMP nucleotidase, nucleosidediphosphate kinase and polynucleotide phosphorylase. One of many predictions based on this model is that cells differentiating in the presence of glucose will produce sorocarps with an abnormally high trehalose to cellulose ratio. External perturbation of either the model or of developing cells by glucose increases the levels of sorocarp trehalose and glycogen, 5-fold and 6-fold respectively. Evaluation of the experimental data and the simulation analyses have allowed several predictions to be made concerning the compartmentation of metabolites and the permeability of cells to glucose during differentiation.
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PMID:Fourth expansion and glucose perturbation of the Dictyostelium kinetic model. 55 94

Homopolymers of etheno CMP have been prepared by the action of polyribonucleotide phosphorylase upon etheno CDP. At alkaline pH the optical properties are consistent with a structure consisting of partially helical single-stranded chains whose helical regions are stabilized by base stacking. At acid pH the degree of helicity increases markedly. The degree of cooperativity displayed by the helix leads to coil transition induced by pH or temperature is less than for the case of polyribocytidylic acid. In the presence of acridine orange the alkaline form develops a strong extrinsic CD spectrum.
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PMID:Physical properties of poly (3,N4-ethenocytidylic acid). 62 74

Procedures for the controlled addition of one or more deoxyribonucleotide residues to the 3' end of an oligodeoxyribonucleotide primer are described. Polynucleotide phosphorylase (EC 2.7.7.8), purified from Escherichia coli B, catalyzes the reaction using a deoxyribonucleoside 5'-diphosphate as substrate, with Mn2+ as cofactor. Reaction occurs rapidly in aqueous solution, and no protecting groups are required, simplifying recovery and purification of the products. The concentrations of sodium chloride and manganous chloride in the incubation mixture are critical to obtaining good yield of the required product. Primers of chain length from 3 to 12 have been extended by up to 9 deoxyribonucleotide residues to obtain oligodeoxyribonucleotides of chain length up to 13. Yields of single addition products varied from 8 to 59%. Factors which influence these yields are discussed. The effects of added polyamines and some organic solvents on the reaction are described. Spermidine or dimethylsulfoxide in the incubation medium tend to favor the addition of several residues of deoxyribonucleotide to the primer.
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PMID:Enzymatic synthesis of oligodeoxyribonucleotides of defined sequence. 63 85

The genomic RNA of human coronavirus strain 229E (HCV 229E) migrated on polyacrylamide gels as a single peak with a mol. wt. of 5.8 X 10(6). Denaturation of the genome with formaldehyde did not alter its electrophoretic mobility, which suggests that the HCV 229E genome is a single-stranded molecule. At least 30% of the genomic RNA was shown to contain covalently attached polyadenylic acid [poly(A)]sequences by binding the RNA to an oligo(dT)-cellulose column. These poly(A) tracts were shown to be about 70 nucleotides in length by measuring the resistance to digestion of HCV 229E RNA with pancreatic and T1 RNases. Finally, the genomic RNA was shown to terminate at or near the 3'-terminus on the basis of its susceptibility to polynucleotide phosphorylase.
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PMID:The genome of human coronavirus strain 229E. 66 Jan 65

2'-Deoxy-2'-fluoroadenosine was chemically transformed to its 5'-diphosphate and polymerized with polynucleotide phosphorylase to give poly(2'-deoxy-2'-fluoroadenylic acid) [poly(Af)]. Polymerization proceeded smoothly as in the case of poly(A) and the yield of the polymerization was 55%. The UV absorption spectra of poly(Af) closely resembled those of poly(A) and the hypochromicity was 32% at pH 7.0. The CD profile at 25 degrees and neutrality showed similar pattern to that of other poly(2'-deoxy-2'-halogenoadenylic acids) with somewhat larger [theta] values both in the positive and negative maxima. Acid titration of poly(Af) showed a transition point at pH 5.2 and the Tm of the acid form was 37 degrees which was significantly lower than that of poly(A), but similar to that of poly(2'-azido-2'-deoxyadenylic acid). Poly(Af) formed 1:1 and 1:2 complexes with poly-(U) having Tm of 49 degrees and 62 degrees at 0.04M and 0.15M Na(+) concentration, respectively. Poly(Af) also formed a 1:2 complex with poly(I) and its Tm was 36 degrees at 0.05M Na(+) concentration. These data showed that poly(Af) has rather similar properties to those of poly(A), but not to poly(dA).
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PMID:Polynucleotides. LII. Synthesis and properties of poly(2'-deoxy-2'-fluoroadenylic acid). 67 38

We report simplified methods for large scale enzymatic synthesis of oligoribonucleotides using polynucleotide phosphorylase. The main features of the method are use of RPC-5 chromatography, including chromatography at two pH values to deal with the problem of primer phosphorolysis, rapid dialysis for large scale desalting, simplified methods for enzyme removal, and high resolution 1H and 31P NMR for product identification and demonstration of purity. The capacity of the method is adequate to allow beginning with grams of material in the first polymerization step, so that product yields of several milligrams, sufficient for many physical studies, are possible after as many as three separate polymerization reactions.
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PMID:Simplified methods for large scale enzymatic synthesis of oligoribonucleotides. 67 55

Poly (2'-deoxy-2'-fluoroinosinic acid) [ poly(If)] was synthesized by polymerization of 2'-deoxy-2'-fluoroinosine 5'-diphosphate catalyzed by Escherichia coli polynucleotide phosphorylase. Although the UV absorption properties of poly(If) closely resembled those of poly(I), thermal melting curves at Na+ concentrations of 0.15M and 0.75M suggested two ordered structures for poly(If) neutral form. CD psectra taken at 0.15M Na+ concentration showed rather larger amplitudes in both a peak at 273 nm and a trough at 246 nm, suggesting rather strong vertical stacking of bases. When complexed with poly(C), poly(If) forms a double-stranded complex, poly(If).poly(C) which has Tm's higher by 10-20 degrees than those of poly(If).poly(C) measured under the same conditions. The CD spectrum of this complex resembled that of poly(I).poly(C). The effect of the fluorine atom at the 2'-position on thermal stability of polynucleotides is discussed.
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PMID:Polynucleotides. LVI. Synthesis and properties of poly(2-deoxy-2'-fluoroinosinic acid). 70 58

A possible role of polynucleotide phosphorylase (PNPase) in the destruction of poly-A fragments located at the 3'-OH end of mRNA from rat liver polyribosomes was studied. Using hybridization of mRNP particles and mRNA with poly-U Sepharose 4B, it was found that polyribosomal PNPase in vitro destroys the poly-A sequences of approximately 25% of poly-A+ mRNA during the first minutes of incubation at a high rate. The destruction of the poly-A fragment of mRNA by PNPase is incomplete, since part of it is presumably protected by proteins firmly bound to the poly-A sequences of mRNA.
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PMID:[Destruction of mRNA poly-A sequences by polynucleotide phosphorylase in rat liver microsomes]. 73 13

On incubation of cells of E. coli B and MRE 600 (logariphmic phase of growth), treated with toluene in presence of a mixture 14C-nucleoside-5'-diphosphates, Mg2+ or Mn2+ and tris HCl buffer pH 8.0, intracellular synthesis of heteropolyribonucleotide was observed. The synthesis was catalyzed by polynucleotide phosphorylase (PNPase, E. C. 2.7.7.8). An increase in GDP concentration in the medium distinctly decreased the incorporation of other NDP into the polymer (poly-AGUC). If the ratio of ADP, UDP, CDP, GDP in the medium was 1:1:1:0.2, the composition of nitrogenous bases in the heteropolymer produced reflected completely the NDP concentrations in the incubation mixture. Addition of different amino acids (1-lysine, 1-histidine, glycine, 1-phenylalanine) and their mixtures stimulated poly-AGUC synthesis markedly and caused an appreciable alteration in the nucleotide composition of the poly-AGUC synthesized. This phenomenon resembled the effect of amino acids on the activity of partially purified PNPase and on RNA synthesis, catalized by the enzyme in vitro. These data suggest that in bacterial cell, i. e. in vivo, PNPase synthesizes specific RNA polyribonucleotide sequences, participating in protein synthesis or in its regulation.
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PMID:[Nucleotide composition of RNA, synthesized by polynucleotide phosphorylase, in toluene-treated cells of Escherichia coli]. 76 93

The 6-aza analogues of toyocamycin and sangivamycin were prepared as potential cytotoxic agents. The toyocamycin analogue (4-amino-1-(beta-D-ribofuranosyl)pyrazolo[3,4-d]pyrimidine-3-carbonitrile) could not be obtained directly from its O-acetylated precursor but was accessible via 4-amino-1-(beta-D-ribofuranosyl)pyrazolo[3,4-d]pyrimidine-3-thiocarboxamide. The identity of the nitrile was verified by its ultraviolet, infrared, and mass spectra, and by its conversion to the corresponding 3-carboxamide and thiocarboxamide when treated with water or hydrogen sulfide, respectively. Bioassay of the synthetic compounds in comparison with 4-amino-1-(beta-D-ribofuranosyl)pyrazolo[3,4-d]pyrimidine (6-azatubercidin) and 4-amino-2-(beta-D-ribofuranosyl)pyrazolo[3,4-d]pyrimidine revealed that the 3-thiocarboxamido derivative was more cytotoxic to the growth of mouse fibroblasts than 6-azatubercidin, effecting killing of 3T6 cells at less than or equal to 1 mug/ml. 4-Amino-1-(beta-D-ribofuranosyl)pyrazolo[3,4-d]pyrimidine (but not its 2-ribofuranosyl isomer) was shown to act as a substrate for adenosine deaminase from calf intestinal mucosa with an apparent Km of 125 (vs. 20 for adenosine) and the corresponding 5'-diphosphate of 6-azatubercidin was polymerized by polynucleotide phosphorylase (Micrococcus luteus) in the presence of Mn2+ to afford a homopolymer and copolymers with adenosine. The copolymers directed the binding of [3H]lysyl-tRNA to the A-site of ribosomes from Escherichia coli, but could not be used for the synthesis of polylsine in a cellfree system. The copolymer consiting of adenosine and 6-azatubercidin in a 2:1 ratio was found to form a 1:1 complex with poly(uridylic acid) at 4degreesC.
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PMID:Synthesis and biological activity of pyrazolo[3,4,-d]pyrimidine nucleosides and nucleotides related to tubercidin, toyocamycin, and sangivamycin. 76 33


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