Function of Cu²⁺ on the DNA-Breaking Actions of Ascorbic Acid and Triose Reductone

Abstract

The role of Cu²⁺ on the DNA-breaking action of ascorbic acid (AsA) and triose reductone (TR) was studied with an agarose slab gel electrophoretic analysis. AsA and TR decomposed calf thymus DNA which had been pretreated with Cu²⁺, and their decomposing activity was proportional to the concentration of Cu²⁺ bound to the DNA. The DNA-Cu²⁺ complex had the ability to oxidize reductones. AsA and TR also decomposed the pretreated DNA with Cu²⁺ more markedly than that pretreated with Cu²⁺ and successively with EDTA. The DNA-breaking activity of AsA and TR showed no Cu²⁺-concentration dependency. The maximal fragmentation of DNA occurred at the concentration ratio of DNA and Cu²⁺ of 4: 1. Excess concentration of Cu²⁺ decreased the activity of reductones. The present results indicate that the binding of Cu²⁺ to DNA molecules is also essential for the DNA-breaking action of AsA and TR in the presence of Cu²⁺ and that Cu²⁺ bound to DNA molecules has more effective promoting activity than free Cu²⁺