CAREER: Breaking Down the Structure-function Relationships in Enzymes that Catabolize Chlorophyll

With the support of the Chemistry of Life Processes (CLP) program in the Division of Chemistry, Jennifer Bridwell-Rabb from the University of Michigan is investigating the structure and mechanisms of action of enzymes involved in chlorophyll degradation. Chlorophyll pigments are integral to photosynthesis, a process by which organisms convert light energy into chemical energy. Paradoxically, the same properties that poise chlorophyll pigments to harness sunlight, also have the potential to negatively impact the health of photosynthetic organisms. Therefore, akin to the enzymes involved in synthesizing chlorophyll, the enzymes involved in degrading this pigment are also critical. Chlorophyll degrading enzymes protect organisms from toxic pigment accumulation, support the ability of crops to resist environmental stressors, and impact the lifetimes of fruits and vegetables. Despite the plethora of known chlorophyll degrading enzymes, there is a critical gap in knowledge regarding how these enzymes perform their functions. Therefore, this project is aimed at training researchers to use structural biology and enzymology to illuminate the mechanisms of key degradative enzymes. Furthermore, this project will train researchers to accessibly communicate science to a general audience, and through educational outreach, will engage middle school students, as well as a greater global population, in the fundamental science of photosynthesis. This research project is specifically focused on using structural, biochemical, and biophysical techniques to (i) establish structure-function relationships in chlorophyll-degrading enzymes, (ii) reveal mechanistic details integral to chlorophyll catabolism, and (iii) identify the strategies that photosynthetic organisms use to synchronize chlorophyll degradation with cellular and environmental conditions. To accomplish these goals, degradative enzymes of interest will be identified, isolated, structurally characterized, and mechanistically studied. This work has potential to resolve deficits in our mechanistic understanding of how chlorophyll pigments are degraded in a calculated manner. In the long term, the findings of this project could inform strategies to manipulate or harness chlorophyll degradation to improve crop growth, elongate the lifetime of produce, and protect photosynthetic organisms from biotic and abiotic stressors. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.