Phosphoglycerate mutases: stereochemical course of the phosphoryl group transfers catalyzed by the cofactor-dependent enzyme from rabbit muscle and the cofactor-independent enzyme from wheat germ.

2-[(R)-16O,17O,18O]Phospho-D-glycerate has been synthesized and used to determine the stereochemical course of each of the two mechanistic classes of phosphoglycerate mutases. The enzyme from rabbit muscle requires 2,3-bis-phospho-D-glycerate as a cofactor and catalyzes an intermolecular phosphoryl group transfer reaction. The enzyme from wheat germ requires no cofactor and catalyzes an intramolecular transfer of the phosphoryl group. We have shown that the reaction catalyzed by each of these enzymes proceeds with overall retention of the configuration at phosphorus. This stereochemical result is consistent with a double-displacement pathway involving a single phosphorylenzyme, for each of the catalyzed reactions.