Acetate kinase: a triple-displacement enzyme.

Facts relating to the mechanism of phosphoryl transfer by acetate kinase (ATP:acetate phosphotransferase, EC 2.7.2.1) are reviewed. They point to the existence of at least one experimentally established phosphoenzyme (E-P) intermediate on the reaction pathway. Sterically, the phosphoryl transfer occurs with a net inversion of the configuration of the phosphorus atom. These facts are best in accord with a triple-displacement mode of action for acetate kinase, with two E-P intermediates and three steric inversions on phosphorus. It follows that a second E-P for acetate kinase must exist.