Probing the mechanism of enzymatic phosphoryl transfer with a chemical trick.

Abstract

Nucleophilic substitutions at phosphorus comprise one of the most important classes of reactions in biology. Phosphate diester substitution reactions are catalyzed by nucleases and polymerases and are critical in DNA replication and transcription. Phosphate monoester (phosphoryl transfer) reactions are catalyzed by GTPases, ATPases, protein, and small molecule kinases, protein, and small molecule phosphatases. These enzymes play diverse roles in energy regulation, cell signaling, ion and small molecule transport, and nucleotide synthesis. There have been intensive efforts to try to understand the details of phosphoryl transfer reactions extending from nonenzymatic (or enzyme model) systems to the mechanisms of the enzymatic reactions, as exemplified by the study by Cho et al. in the current issue of PNAS (1). A full and convincing explanation at the quantum mechanical level has not been made as to why dissociative transition states should be preferred for nonenzymatic phosphoryl transfer reactions.