title: Poly(adenosine diphosphate ribose) polymerase in Physarum polycephalum.
abstract: 1. The isolated nuclei of the slime mould Physarum polycephalum contain an enzyme that will incorporated [adenine-3H] NAD+ into an acid-insoluble product, which is shown to be poly(ADP-ribose). 2. This incorporation has an optimum pH of 8.2 and a temperature optimum below 10degreesC. 3. Optimum stimulation is given by 15 mM-Mg2+. 4. 2-Mercaptoethanol or dithiothreitol also stimulates the incorporation, the latter at an optimum concentration of about 1 mM. 5. Under optimum conditions the Km value for the reaction is 0.28 mM at 15degreesC. Nicotinamide inhibits the incorporation with a Ki of 5.7 muM. 6. Exogenous DNA stimulates the incorporation by about 100%. 7. Preincubation of the nuclei with deoxyribonuclease, but not with ribonuclease, almost completely inactivates the incorporation of NAD+. 8. The enzyme is unstable at both 0degrees and 15degreesC in the absence of dithiothreitol. The presence of dithiothreitol at a concentration of 1 mM stabilizes the enzyme at both these temperatures. 9. The activity of this enzyme per nucleus was shown in three separate experiments to fall by about one-half in early S phase and then to rise to its pre-mitotic value after about 3 h, that is in late S phase. 10. The possible physiological function of this enzyme system is discussed.
mesh_terms: D002467:Cell Nucleus / Q000201:enzymology; D004247:DNA / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D008623:Mercaptoethanol / Q000494:pharmacology; D008938:Mitosis; D009235:Myxomycetes / Q000201:enzymology*; D009699:N-Glycosyl Hydrolases / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D009244:NAD+ Nucleosidase / Q000378:metabolism*; D009536:Niacinamide / Q000494:pharmacology; D010804:Physarum / Q000201:enzymology*; D013268:Stimulation, Chemical; D013696:Temperature
chemical_list: D009243:NAD; D009536:Niacinamide; D008623:Mercaptoethanol; D004247:DNA; D009699:N-Glycosyl Hydrolases; D009244:NAD+ Nucleosidase; D008274:Magnesium; D004229:Dithiothreitol