Catalysis of Phosphoryl Transfer from ATP by Amine Nucleophiles

Phosphoryl transfer from the high-energy phosphate donor ATP is ubiquitous in biological chemistry, and nitrogen nucleophiles, especially histidine, often serve as in vivo acceptors of the γ-phosphate of ATP. Nevertheless, nonenzymatic reactions of ATP with amines have not previously been characterized. We have therefore examined phosphoryl transfer from ATP to amines to provide a basis for understanding the analogous enzymatic reactions, and we have compared the rates of these reactions to the rates with oxygen nucleophiles in order to assess whether intrinsically higher reactivities of nitrogen nucleophiles could cause them to be favored over oxygen nucleophiles in covalent catalysis of phosphoryl transfer by enzymes. Reactions of amine nucleophiles are 30-100-fold faster than reactions of oxygen nucleophiles at physiological temperatures. Thus, the reactivity of amines, in addition to thermodynamic and evolutionary factors, may have played a role in the selection of nitrogen nucleophiles for use in biological phosphoryl-transfer reactions. In the course of these studies, the reaction of fluoride ion with ATP tetraanion was also observed. Surprisingly, the rate constant for the reaction of fluoride ion with ATP is similar to rate constants for reactions of uncharged amine and oxygen nucleophiles with ATP, providing no support for proposals that reactions of ATP and other phosphoryl anions with anionic nucleophiles are prevented by electrostatic repulsion in aqueous solution.