Phosphoenolpyruvate synthetase and pyruvate, orthophosphate dikinase: stereochemical consequences at both the .beta.-phospho and .gamma.-phospho groups of ATP

Abstract

[(R)-16O,17O,18O]Phosphoenolpyruvate and adenosine 5'-O-[(gamma S)-beta gamma-17O,gamma-17O,18O](3-thiotriphosphate) have been synthesized and used to determine the stereochemical course of the several displacements at phosphorus catalyzed by phosphoenolpyruvate synthetase and by pyruvate, orthophosphate dikinase, two enzymes that catalyze the formation of phosphoenolpyruvate from pyruvate and ATP. The catalytic mechanisms for each of these enzymes are believed to involve both phospho- and pyrophospho-enzyme intermediates. The stereochemical results are entirely in accord with these pathways: the beta-phospho group of ATP suffers overall retention of configuration that is presumably the consequence of two displacements with inversion, and the gamma-phospho group of ATP gamma S suffers inversion of configuration that is most probably the consequence of a single displacement at this center.