Abstract
1. The synthetic reactions by a novel ribonuclease, RNase U2 [ribonucleate purinenucleotido-2'-transferase (cyclizing)] were studied. The yield of adenylyl-(3', 5')-uridine amounted to 37% when adenosine 2', 3'-cyclic phosphate (A cyclic-p) and uridine were incubated with RNase U2. Furthermore 58% of A cyclic-p remained unchanged. RNase U2 was, thus, proved to be a useful tool for the synthesis of oligonucleotide.
2. The yield of ApN was influenced by various factors, such as temperature, in-cubation time, pH, enzyme concentration and phosphate acceptors. It was found that a lower temperature gave a larger amount of the product, reducing the competing hydrolytic activity. The yield of ApN decreased according to the type of phos-phate acceptors in the following order: cytosine>uridine>glyoxal G cyclic-p, inosine>adenosine> 2'(3')-cytidylate>2'(3')-guanylate.
3. ApG cyclic-p, a substrate of RNase N, [EC 2. 7. 7. 26] for the synthesis of oligo ApGp, was also prepared by RNase U2 with 10% yield.
4. Oligoadenylic acids consisting of two to five adenylyl residues were synthesized by RNase U2 and fractionated by DEAE-Sephadex column chromatography in the presence of 7M urea. The yield of polymerized products was about 22% including ApA cyclic-p (14.1%), ApAp (2.7%) and trimer (5.4%).
