Breaking action of ascorbic acid on nucleic acids

The lowering of the viscosity of DNA solution was caused by the action of AsA or EA and facilitated in the presence of CU2+. However, the action of AsA-3-P was very weak. By sucrose density gradient centrifugation, it was observed that single- and double-strand scissions of DNA were provoked by AsA or EA and enhanced with Cu2+, while only a single-strand scission was caused by AsA-3-P and Cu2+. Similar action of AsA or AsA-3-P was also observed for RNA. Thus, the result indicates that the enediol group of AsA takes an essential part in the breakage of nucleic acids, and Cu2+ enhances the action. It was shown that Apu was mainly decomposed by AsA, whereas Apy not, suggesting that some pyrimidine cluster may be one of the regions attacked by AsA. During the reaction with DNA, the reducing activity of AsA decreased first to some extent and then increased, whereas the reducing activity of AsA-3-P was much lower than that of AsA and decreased steadily. The priming activity of DNA for DNA polymerase was changed after treatment with AsA according to the condition. It was enhanced when DNA was treated under mild conditions but decreased with severer action.