The rate of spontaneous cleavage of the glycosidic bond of adenosine

• Published in: Bioorganic chemistry Vol. 38; no. 5; pp. 224 - 228
• Main Authors: Stockbridge, Randy B., Schroeder, Gottfried K., Wolfenden, Richard
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2010
• Subjects: Adenosine; Adenosine - chemistry; Glycoside cleavage; Hydrogen-Ion Concentration; Hydrolysis; Kinetics; Nucleoside N-ribohydrolase; Rate enhancement; Ricin; Thermodynamics of activation; Thermodynamics of activation; Adenosine; Ricin; Rate enhancement; Nucleoside N-ribohydrolase; Glycoside cleavage
• ISSN: 0045-2068; 1090-2120; 1090-2120
• DOI: 10.1016/j.bioorg.2010.05.003

We show that hydrolysis of the glycosidic C N 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. 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 × 10 12-fold.