Phosphoryl transfer enzymes and hypervalent phosphorus chemistry

The coordination tendencies of phosphorus to form a hexacoordinated state from a pentacoordinated state, which might assist in describing the mechanistic action of phosphoryl transfer enzymes, are delineated. The factors discussed include substrate and transition or intermediate state anionicity, hydrogen bonding, packing effects, that is, van der Waals forces, the ease of formation of hexacoordinate phosphorus from lower coordinate states, and the pseudorotation problem common to nonrigid pentacoordinate phosphorus. In view of the work reported in this Account and recent work on enzyme promiscuity and moonlighting activities, it is suggested that donor action should play a role in determining active site interactions in phosphoryl transfer enzyme mechanisms.