Hydrolysis of nucleoside phosphates: IV.* The metal ion - nucleic base interaction in the Cu2+-promoted dephosphorylation of the 5′-di- and 5′-triphosphates of cytidine, inosine and guanosine, and their protection toward hydrolysis by coordination to Cu(2,2′-bipyridyl)2+
✍ Scribed by Helmut Sigel; David H. Buisson; Bernhard Prijs
- Publisher
- Elsevier Science
- Year
- 1975
- Weight
- 946 KB
- Volume
- 5
- Category
- Article
- ISSN
- 0006-3061
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✦ Synopsis
The dephosphorylation of CTP, GTP, ITP, ATP. CDP, GDP, IDP and ADP was characterized by measuring the first-order rate constant (SOa; l = 0.1, NaCIO,) in dependence on pH (2 to 10). Except with CTP and CDP, the reactions are significantly accelerated by Cu" and pass through pH optima. By computing the pH dependence of the distribution of the several species present in the nucleotide (NP) systems, it is shown that the most reactive species is Cu(NP). Cu(NP-H), where N(1) is deprotonated, is somewhat less reactive. In both types of complexes, a metal ion-nucleic base interaction, which is responsible for the increased reactivity, occurs, i-e-, macrochelates involving the phosphate chains and the base moieties are formed_ in accord herewith, CTP and CDP are rather stable as the coordination tendency of the cytosine moiety is small. Furthermore, in the ternary complexes Cu(2,2'bipyridyl)(NP) and Cu-(2,2'-bipyridyl)(NP-H), where the formation of a macrochelate is inhibited, the nucleotides are protected. The structure-*For Part III see I l] _ Ab6rev~arions.