The goals of this project are to provide definitive answers to a range of structural and mechanistic questions in enzymology. By using multiple experimental approaches, Dr. Villafranca hopes to reach a deeper level of understanding of enzyme catalysis, especially in the relationship of structure to function. Dr. Villafranca will focus on the study of enzymes that involve different types of group transfer reactions with ATP. Primarily, the enzyme CTP synthetase will be studied with some additional work on GMP synthetase and pyruvate phosphate dikinase. By using several structural and kinetic approaches he will investigate the nature and relative free energies of the central enzyme complexes for the reactions catalyzed by these enzymes. Exploration of the identity of enzymic groups and the rate of formation and breakdown of intermediates in this enzymatic reaction will provide a set of data with which to make mechanistic deductions about the catalytic efficiency of group transfer reactions.