Studies on the Polymer of Adenosine Diphosphate Ribose

Abstract

A particulate fraction obtained from rat liver nuclei is capable of polymerizing the adenosine diphosphate ribose moiety of nicotinamide adenine dinucleotide with the simultaneous release of nicotinamide. Comparative studies on this reaction and the nicotinamide mononucleotide-dependent adenosine triphosphate polymerization, originally described by Chambon, Weill, and Mandel, and later confirmed partly by Fujimura and Sugimura, reveal that both reactions are fundamentally identical and that NAD but not ATP is the immediate substrate for the polymerization. The activity, as assayed with NAD as the substrate, is essentially localized in nuclei from various organs and is markedly decreased by prior incubation of the nuclear preparation with pancreatic deoxyribonuclease but not by pancreatic ribonuclease and T₁ RNase, nor is it affected by the addition of actinomycin D or any of the nucleoside triphosphates. The reaction product is resistant to either mild alkaline hydrolysis, pancreatic DNase, RNase, T₁ RNase, Neurospora NADase, or various proteinases. Upon treatment with venom phosphodiesterase, more than 95% of this material is made acid-soluble to produce a single compound possessing 1 mole of adenine, 2 moles of ribose, and 2 moles of phosphate. Preliminary analysis of the reaction product suggests that it may be a hitherto unknown macromolecule composed of repeating ADP-ribose units.