The nonenzymatic activation of acetate by adenosine triphosphate-bivalent metal chelates.

reaction, which occurs under mild conditions and at low concentrations of reactants, is absolutely dependent on the presence of bivalent metal ions, and is stimulated by univalent metal ions. The most effective bivalent metal ion was found to be Ca++. When Mn++ ion was used to satisfy the bivalent metal ion requirement, the most effective univalent metal ion was found to be Kf. The reaction was formulated as a nucleophilic attack of orthophosphate on a chelate of ATP and bivalent metal. Chelation increases the electrophilic character of the phosphorus atoms of ATP, and thus facilitates the nucleophilic attack by orthophosphate. The bivalent metal ion also screens the negative charges of ATP from those of the attacking molecule. Alkali metal ions stimulate the reaction by neutralizing the residual negative charges of the active chelate (l-3). The influence of metal ions on the acceptor molecule (orthophosphate) has not so far been studied. Carboxylic acids such as acetate, glycine, and fl-alanine can act as acceptors in place of orthophosphate. When the reaction is run in the presence of hydroxylamine, the product can be trapped as a hydrosamate (Equation 2). Nonenzymatic trans-