The polymerization of adenosine 5'-diphosphate-ribose moiety of NAD by nuclear enzyme. II. Properties of the reaction product.

Abstract

Abstract The radioactive acid-insoluble material, Product I, which was formed by rat-liver nuclear preparation from labeled NAD or labeled ATP with nicotinamide mononucleotide, has been partially purified. It has a peak at 3 S with sucrose density-gradient centrifugation, and a density of around 1.57 with Cs 2 SO 4 equilibrium density-gradient centrifugation. Product I was converted into the acid-soluble form by snake-venom phosphodiesterase. Product I was not digested by micrococcal nuclease, spleen phosphodiesterase, potato phosphodiesterase, potato nucleotide pyrophosphatase, spleen NAD nucleosidase, or trypsin. The radioactive acid-soluble substance, Product II, which was released by venom-phosphodiesterase digestion, was isolated from a Dowex 1 formate column. Product II showed absorption maxima at 261, 259, and 258 mμ under alkaline neutral and acidic conditions, respectively. The molar ratio of adenine (as adenosine), ribose, phosphorus and periodate consumption was 1:2:2:1. All phosphates were converted to inorganic phosphate by acid-phosphatase digestion. Structures of Products I and II were proposed.