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, o ften serve as in vivo accepters of the gamma-phosphate of ATP. Nevertheless , nonenzymatic reactions of ATP with amines have not previously been charac terized. 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 nuc leophiles in order to assess whether intrinsically higher reactivities of n itrogen nucleophiles could cause them to be favored over oxygen nucleophile s in covalent catalysis of phosphoryl transfer by enzymes. Reactions of ami ne nucleophiles an 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 s election of nitrogen nucleophiles for use in biological phosphoryl-transfer reactions. In the course of these studies, the reaction of fluoride ion wi th ATP tetraanion was also observed. Surprisingly, the rate constant for th e reaction of fluoride ion with ATP is similar to rate constants for reacti ons of uncharged amine and oxygen nucleophiles with ATP, providing no suppo rt for proposals that reactions of ATP and other phosphoryl anions with ani onic nucleophiles are prevented by electrostatic repulsion in aqueous solut ion.