SYNTHESIS OF GUANYLYL-(3',5')-NUCLEOSIDES AND OLIGOGUANYLIC ACIDS BY RIBONUCLEASE N1

1. 1. The synthesis of guanylyl-(3′,5′)-nucleoside by ribonuclease N1 (ribonuclease guanine nucleotido-2′-transferase (cyclizing), Neurospora crassa, EC 2.7.7.26) was studied. The yield of guanylyl-(3′,5′)-uridine amounted to 27% in regard to guanosine 2′,3′-cyclic phosphate (G > p) added. Then 55% of G > p remained unchanged. Thus ribonuclease N1 was proved to be a more useful tool than ribonuclease T1 (EC 2.7.7.26) for the synthesis of oligonucleotides. 2. 2. The yield of guanylyl-(3′,5′)-nucleoside by ribonuclease N1 depends on temperature, pH, incubation time, substrate concentration, enzyme concentration and the nature of acceptor. Low temperature and neutral pH gave a large amount of the product, reducing the competing hydrolytic activity. The effect of the nature of phosphate acceptor on the yield of guanylyl-(3′,5′)-nucleosides was in the following order: cytosine > uridine > adenosine. 3. 3. Oligoguanylic acids consisting of two to six guanylyl residues were synthesized by ribonuclease N1 and fractionated by the procedure of DEAE-Sephadex column chromatography in the presence of 7 M urea. © 1969.