Transition State Analogue Structures of Human Phosphoglycerate Kinase Establish the Importance of Charge Balance in Catalysis

摘要

Abstract: Transition state analogue (TSA) complexes formed by phosphoglycerate kinase (PGK) havenbeen used to test the hypothesis that balancing of charge within the transition state dominates enzyme-ncatalyzed phosphoryl transfer. High-resolution structures of trifluoromagnesate (MgF3 ) and tetrafluoro-naluminate (AlF4 ) complexes of PGK have been determined using X-ray crystallography and 19F-basednNMR methods, revealing the nature of the catalytically relevant state of this archetypal metabolic kinase.nImportantly, the side chain of K219, which coordinates the -phosphate group in previous ground statenstructures, is sequestered into coordinating the metal fluoride, thereby creating a charge environmentncomplementary to the transferring phosphoryl group. In line with the dominance of charge balance inntransition state organization, the substitution K219A induces a corresponding reduction in charge in thenbound aluminum fluoride species, which changes to a trifluoroaluminate (AlF3n0) complex. The AlF3n0 moietynretains the octahedral geometry observed within AlF4 TSA complexes, which endorses the proposal thatnsome of the widely reported trigonal AlF3n0 complexes of phosphoryl transfer enzymes may have beennmisassigned and in reality contain MgF3 .