Comparison of Acid- and Enzyme-Catalyzed Cleavage of the Glycosidic Bond of N(7)-Substituted Guanosines

Kinetic parametrs for enzymatic cleavage of the glycosidic bond (phosphorolysis) of ten N(7)-substituted guanosines were determined, and used to establish a structure-activity relation for the Michaelis constants. Results were compared with those for acid-catalyzed cleavage of the glycosidic bonds, and are consistent with a mechanism for phosphorolysis via protonation of the purine ring N(7).