The rate of spontaneous cleavage of the glycosidic bond of adenosine

Previous estimates of the rate of spontaneous cleavage of the glycosidic bond of adenosine were determined by extrapolating the rates of the acid- and base-catalyzed reactions to neutral pH. Here we show that cleavage also proceeds through a pH-independent mechanism. Rate constants were determined as a function of temperature at pH 7 and a linear Arrhenius plot was constructed. Uncatalyzed cleavage occurs with a rate constant of 3.7 × 10−12 s−1 at 25 °C, and the rate enhancement generated by the corresponding glycoside hydrolase is ∼5 × 1012-fold.

We show that hydrolysis of the glycosidic CN bond of adenosine, previously known to be subject to hydrolysis in acid and base, also proceeds through a pH-independent mechanism with a rate constant of 4 × 10−12 s−1 at 25 °C.Figure optionsDownload as PowerPoint slide