Theoretical study of the hydroxyl nucleophilic attack on the 6-aminopyrimidine molecule: functional implications in the reaction mechanism of nucleoside deaminative enzymes

A quantum chemical study of hydroxyl attack on a reduced model of adenosine and cytidine has been performed by using both semiempirical MNDO and ab initio 4-31G methodologies. The biochemical implications of the results obtained on the mechanism of the reaction of both adenosine and cytidine deaminases are extensively discussed in the context of previous theoretical and experimental data. Finally, several possible «microscopic» reaction mechanisms for these enzymes are suggested