PROJECT SUMMARY Recent advances in ‘omics-based approaches allow virtually any scientist to perform powerful genome-wide, transcriptome-wide and proteome-wide analyses of normal tissue, diseasedtissue, or even single cells. The information provided by these analyses has afforded important insight into cellular changes that occur as a consequence of development, disease and risk factors associated with disease, and the identification of potential targets for disease intervention. Yet, all too commonly, the vast majority of ‘omics studies enable only inferences regarding the ultimate effect of the observation on protein function. For example, many researchers routinely infer that an increase in abundance either at the transcript or protein level correlates with a corresponding increase in that particular protein’s function; but this is not necessarily the case. In reality, the function of a protein is not simply determined by its mRNA or protein abundance, but rather by the culmination of the cell’s ability to fold the protein appropriately, traffic it to the proper cellular/extracellular locale, and the presence of inhibitors, activators, and/or cofactors. To overcome these inherent limitations of conventional ‘omics approaches, a unique chemical- biology approach called activity-based protein profiling (ABPP) has been used to provide functional protein activity data. Towards this end, in this exploratory/developmental project, we will assess i) the utility of ABPP to determine whether age-related retinal alterations ultimately affect protein function in a physiologic context and ii) whether we can leverage newly designed, enzyme-specific ABPP probes to yield real-time enzyme activity in vivo. Successful completion of this project will positively impact our knowledge of ocular enzymes and will provide additional tools for interrogating the intricate biology underlying incurable age-related and inherited eye diseases.