Active Species for Ce(IV)-Induced Hydrolysis of Phosphodiester Linkage in cAMP AND DNA

The hydrolysis of cyclic adenosine 3′,5′-monophosphate and 2′-deoxythymidylyl(3′-5′)2′-deoxythymidine by Ce(NH₄)₂(NO₃)₆ was kinetically studied. The rate of hydrolysis was fairly proportional to the concentration of [Ce ^IV ₂ (OH)₄]⁴⁺, showing that this is the catalytically active species. According to quantum-chemical calculation, the two Ce(IV) ions in this [Ce^IV ₂(OH)₄]⁴⁺ cluster are bridged by two OH residues. Upon the complex formation with H₂ PO₄ ⁻ (a model compound for the phosphodiesters), these two Ce(IV) ions bind the two oxygen atoms of the substrate and enhance the electrophilicity of the phosphorus atom. The catalytic mechanism of Ce(IV)-induced hydrolysis of phosphodiesters has been proposed on the basis these results.

Keywords:

• Artificial nuclease
• Cerium
• DNA cleavage
• Enzyme models
• Phosphodiester hydrolysis

Acknowledgments

This work was partially supported by the Bio-oriented Technology Research Advancement Institution. The support by a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan is also acknowledged.

This article is dedicated to Professor Eiko Ohtsuka on the occasion of her 70th birthday.

Current address for Naoya Takeda: Consolidated Research Institute for Advanced Science and Medical Care, Waseda University, Shinjuku-ku, Tokyo 162-0041, Japan.