Nucleotide exchange reactions catalysed by ribonuclease and spleen phosphodiesterase. II. Synthesis of polynucleotides.

In the preceding paper (Heppel & Whitfeld, 1955) evidence was presented that at least two different phosphodiesterases, namely ribonuclease and spleen phosphodiesterase, can catalyse synthetic and exchange reactions involving nucleotide residues. The simple alcohols, methanol and ethanol, were shown to be capable of acting as acceptors in these reactions in which nucleoside alkyl phosphates are formed from the corresponding benzyl phosphate and an alcohol, and also, in the case of ribonuclease only, from pyrimidine nucleoside-2':3' phosphates (pyrimidine cyclic nucleotides) and an alcohol. The possibility of compounds other than simple alcohols acting as acceptors in this type of reaction has now been examined. It will be demonstrated that cyclic nucleotides and ribonucleosides can act as acceptors for donor nucleotide residues in the presence of ribonuclease to form compounds such as cyclic dinucleotides, cyclic trinucleotides, dinucleoside phosphates and trinucleoside diphosphates. The spleen enzyme catalyses analogous reactions with the exception of those involving nucleoside-2':3' cyclic phosphates, which do not participate in spleen phosphodiesterase-catalysed transfer reactions. Furthermore, in these reactions both enzymes exhibit the same substrate specificity as they do in their hydrolytic reactions. A preliminary report of part of this work has already been published (Heppel, Whitfeld & Markham, 1954).