Hydrolysis of DNA and RNA by lanthanide ions: Mechanistic studies leading to new applications

A few years ago, the remarkable catalytic activity of lanthanide ions for the hydrolysis of nucleic acids was discovered. With Ce(IV), DNA was hydrolysed under physiological conditions. For RNA hydrolysis, the last three lanthanide ions (Tm(III), Yb(III), and Lu(III)) are superb. Furthermore, artificial restriction enzymes for site-selective scission of DNA and RNA, essential tools for the future biotechnology, have been prepared by using the lanthanide complexes. The present article emphasizes the mechanistic aspects of the catalyses of these metal ions. Both DNA hydrolysis and RNA hydrolysis involve the cooperation of acid catalysis (by metal ion and/or metal-bound water) and base catalysis (by metal-bound hydroxide). The magnitudes of contributions of these catalyses, as well as the positions where they work, are primarily governed by the relative height of the energy-barrier for the formation of the pentacoordinated intermediate and that for its breakdown. The following conclusions have been obtained on the basis of various kinetic and spectroscopic evidence: (1) for the hydrolysis of both DNA and RNA, the catalytically active species are dinuclear hydroxo-clusters, (2) Ce(IV) enormously activates DNA and promotes the formation of the pentacoordinated intermediate, and (3) the catalysis for RNA hydrolysis is mainly ascribed to the promotion of breakdown of the pentacoordinated intermediate.