The inherent flexibility of biological macromolecules plays a critical role in their function. This is especially true in the case of enzymes, as these proteins must be able to alter their molecular structures in order to recognize substrates and release products. While they have been shown to be critical for understanding how enzymes function, the exact roles of these structural dynamics are still largely unknown. I have used Nuclear Magnetic Resonance (NMR) Spectroscopy to study the impact of these structural fluctuations for enzyme function in two dramatically different systems: RNA Ligase 10C, a novel enzyme derived via in vitro selection, and the ubiquitous eukaryotic signaling enzyme cAMP-dependent Protein Kinase A (PKA). Despite the variation in their structures and function, I have nonetheless been able to demonstrate the importance of the conformational dynamics of structural elements involved in both systems, suggesting that this is a universal phenomenon, essential for function in all enzymes.