A COMPARATIVE STUDY OF HYDROLYSIS RATES OF 2′-DEOXYADENOSINE AND ADENOSINE 5′-TRIPHOSPHATES AND 5′-DIPHOSPHATES

Abstract

Abstract Rates of hydrolysis of 2′-deoxyadenosine 5′-triphosphate and 5′-diphosphate, dATP and dADP, are measured in 0.01 M aqueous solutions at 70°C, in the pH range 0–9, and are compared with previously obtained data for adenosine 5′-triphosphate and 5′-diphosphate, ATP and ADP. Above pH 5 the hydrolysis involves mainly, or exclusively, a cleavage of the polyphosphate chain, probably by an elimination-addition mechanism via the monomeric metaphosphate ion, PO3 −, from the tetraanion, dATP4- and the trianion, dATPH3-. The effect of Mg2+ and Ca2+ ions on the rate of hydrolysis is similar to the effect of these cations on the rate of hydrolysis of ATP. In the pH range 0–4, the hydrolysis involves primarily a cleavage of the N-glycosidic bond to adenine and deoxyribose polyphosphate. This reaction is much faster for the 2′-deoxyribonucleotides containing a purine ring than for the ribonucleotide analogs.