Metal ions nucleic acid hydrolysis

In the following discussions, recent examples of metal-promoted phosphate hydrolysis will be described, whereby one or two metals have been shown to play a key role, and metal ion participation in the hydrolysis process will be assessed. Metal-promoted hydrolysis seems to be a more suitable term than metal-catalyzed hydrolysis, because up to now one cannot find any case of an efficient metal-catalyzed nucleic acid hydrolysis in the literature. In order to hydrolyze a phosphate ester with water, with a half-life of 1 hr, the... 

RNA hydrolysis, 45 285-287, 297-299 metalloenzymes, 45 251-252 bleomycin, 45 252-260, 299 nucleic acid hydrolysis metal ions and, 45 283-285 by oligonucleotide modified with metal complexes, 45 297-299 of phosphodiesters, 45 251, 287-297 by ribozymes, 45 285-287 cleavage by iron bleomycin, 43 140 polymerase, arsonomethyl phosphonate analogue, 44 201-202 substructures, 43 133-134 transfer... 

Hydrolytic catalysis by metal ions is also important in the hydrolysis of nucleic acids, especially RNA (36). Molecules of RNA that catalyze hydrolytic reactions, termed ribozymes, require divalent metal ions to effect hydrolysis efficiently. Thus, all ribozymes are metalloenzymes (6). There is speculation that ribozymes may have been the first enzymes to evolve (37), so the very first enzymes may have been metalloenzymes Recently, substitution of sulfur for the 3 -oxygen atom in a substrate of the tetrahymena ribozyme has been shown to give a 1000-fold reduction in rate of hydrolysis with Mg2+ but no attenuation of the hydrolysis rate with Mn2+ and Zn2+ (38). Because Mn2+ and Zn2+ have stronger affinities for sulfur than Mg2+ has, this feature provides strong evidence for a true catalytic role of the divalent cation in the hydrolytic mechanism, involving coordination of the metal to the 3 -oxygen atom. Other examples of metal-ion catalyzed hydrolysis of RNA involve lanthanide complexes, which are discussed in this volume. 

Chromium, Manganese, Cobalt, Nickel, Ruthenium, Rhodium, Platinum, and Uranium Complexes Metalloporphsrrin Complexes Metal Ions and Nucleic Acid Hydrolysis... 

A. Role of Metal Ions in Enz3rme-Catalyzed Nucleic Acid Hydrolysis... 

The hypothesis that our biological world built on the DNA-RNA-protein central dogma was preceded by an RNA world in which RNA molecules carried both the genetic information and executed the gene functions (through ribozyme activity) is now widely accepted [130]. However, it is also well recognized that RNA due to its vulnerability to hydrolysis - especially as a result of catalysis by divalent metal ions - would not have been able to evolve in a harsh pre-biotic environment Also the formation of RNA under presumed pre-biotic conditions is extremely inefficient It is not so far-fetched to propose that a peptide nucleic acid-like molecule may have been able to function as a form of pre-biotic genetic material since it... 

In the previous chapters the reactivity of metal ions with the monomer units of nucleic acids has been discussed. This section will deal with the binding of transition metals to the polynucleotides. There are also three types of complexes to be expected the metal-ring, the intermediate and the metal chain complex. The effect of the ribose or deoxyribose residue on the stability constants can be neglected since the reactivity of these sugars with cations is extremely low. However, as it will be seen later, the hydrolysis of polyribonucleotides is markedly facilitated by interaction of metal ions with the 2 —OH groups of the ribose. 

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