Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.8 (polynucleotide phosphorylase)
 723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The antigenic composition and molecular structure of the plasma membrane of Streptococcus pyogenes (group A; M type 6) were studied by crossed immunoelectrophoresis (XIE) and other related quantitative immunoelectrophoretic techniques. After establishment of a reference pattern of 29 immunoprecipitates, the relative differences in amounts of individual antigens contained in membranes isolated from cells that were harvested during the exponential or stationary phase of growth were examined. Relative increases and decreases in amounts of individual antigens were estimated from the areas subtended by immunoprecipitates after XIE of Triton X-100 extracts. The asymmetric distribution of antigens on the inner and outer surfaces of the membrane was established in absorption experiments with intact, stable protoplasts. Of the 29 immunoprecipitates, 8 appeared to contain antigens exposed on the outer surface of the membrane, whereas 11 appeared to contain antigens either located on the inner surface or unexposed. Six antigens appeared to have limited exposure on the outer surface, and four others remain to be assigned. Certain immunoprecipitates were characterized with respect to enzymatic activity or interaction with the lectin concanavalin A. Reduced nicotinamide adenine dinucleotide dehydrogenase (EC 1.6.99.3), adenosine triphosphatase (EC 3.6.1.3), and polynucleotide phosphorylase (EC 2.3.7.8) were demonstrated by zymogram techniques. The latter two activities were present within the same immunoprecipitate, suggesting the occurrence of a multienzyme complex. In addition, the areas under the immunoprecipitates containing the three enzymatic activities were not affected by absorption of antimembrane immunoglobulin with intact protoplasts and thus appeared to be located on the inner surface of the membrane. The results from absorption experiments also suggested that the exposure of outer protoplast surface antigens was greater on protoplasts from exponential-phase cells than on those from stationary-phase cells, even when found in increased amounts in the latter.
 ...
PMID:Quantitative immunoelectrophoretic analysis of Streptococcus pyogenes membrane. 16 Aug 91

The reaction of the tetranucleotide, pA-A(2)-A, with 2'(3')-0-(alpha-methoxyethyl)uridine 5'-diphosphate, Mg(2+) ions, and M. luteus polynucleotide phosphorylase followed by mild acid treatment to remove the blocking groups results in a 49% yield of the desired single addition product, pA-A(3)-U, together with smaller amounts of pA-A-U, pA-A-A, pA-A(2)-U, pA-A(2)-A, pA-A(3)-A, pA-A(4)-U, and pA-A(4)-A. The side products are thought to arise from the phosphorolysis of the acceptor molecule by the inorganic phosphate formed in the reaction mixture and from subsequent additions to the various oligonucleotide species by the resulting adenosine 5'-diphosphate. A system developed for the removal of inorganic phosphate as it is formed in the synthesis involves the addition to the reaction mixture of calf spleen nucleoside phosphorylase and nicotinamide riboside and, under these conditions, pA-A(3)-U can be prepared in 90% yield with essentially no side products. Under similar conditions, pA-A(3)-A, pA-A(3)-G, and pA-A(3)-C may be prepared from pA-A(2)-A and the appropriate blocked nucleoside diphosphate in yields of 85-94%. The incubation of pA-A(2)-A alone with polynucleotide phosphorylase exhibits the phenomenon of "transnucleotidation" in that the molecule is partially converted to oligonucleotides of smaller and larger chain lengths. In the presence of the phosphate removal system, however, the tetranucleotide is not attacked by the enzyme, and thus, "transnucleotidation" appears to be simply a combination of phosphorolytic and addition reactions catalyzed by trace amounts of inorganic phosphate contaminating the enzyme and/or the substrate.
 ...
PMID:'Single addition' and 'transnucleotidation' reactions catalyzed by polynucleotide phosphorylase. Effect of enzymatic removal of inorganic phosphate during reaction. 428 Oct 80

Nicotinamide mononucleoside 5'-diphosphate in its reduced form is an excellent substrate for polynucleotide phosphorylase from Micrococcus luteus both in de novo polymerization reactions and in primer extension reactions. The oxidized form of the diphosphate is a much less efficient substrate; it can be used to extend primers but does not oligomerize in the absence of a primer. The cyanide adduct of the oxidized substrate, like the reduced substrate, polymerizes efficiently. Loss of cyanide yields high molecular weight polymers of the oxidized form. Terminal transferase from calf thymus accepts nicotinamide mononucleoside 5'-triphosphate as a substrate and efficiently adds one residue to the 3'-end of an oligodeoxynucleotide. T4 polynucleotide kinase accepts oligomers of nicotinamide mononucleotide as substrates. However, RNA polymerases do not incorporate nicotinamide mononucleoside 5'-triphosphate into products on any of the templates that we used.
 ...
PMID:Enzymatic synthesis of polymers containing nicotinamide mononucleotide. 747 5

Polynucleotide phosphorylase is a prokaryotic enzyme that catalyzes phosphorolysis of polynucleotides with release of nucleotide diphosphates. By taking advantage of this property, we developed a photometric assay for inorganic phosphate. In the presence of polyadenylic acid, phosphate is converted into adenosine 5'-diphosphate (ADP) by this enzyme. ADP then reacts with phosphoenolpyruvate in a pyruvate kinase-catalyzed reaction, thus giving rise to adenosine 5'-triphosphate and pyruvate. Finally, pyruvate oxidizes reduced nicotinamide adenine dinucleotide (NADH) through the action of L-lactate dehydrogenase, with concomitant decrease in absorbance at 340 nm. As expected, in this detection system 1 mol of NADH was oxidized per mole of phosphate. The assay showed an excellent reproducibility, as the standard deviations never exceeded 5%. It also was shown to be unaffected by several compounds that are regarded as major interferents of the traditional colorimetric assays. Absence of interference was also demonstrated when determining phosphate content in different biological samples, such as human serum and perchloric acid extracts from Escherichia coli, yeast, and bovine liver. An E. coli strain overexpressing His-tagged polynucleotide phosphorylase developed in our laboratories allowed quick and straightforward purification of enzyme, making the assay feasible and convenient. Since all other reagents required are inexpensive, the assay represents a cheaper alternative to commercially available phosphate assay kits.
 ...
PMID:Polynucleotide phosphorylase-based photometric assay for inorganic phosphate. 1505 37