Glycogen and starch serve as major energy storage compounds for nearly all- living organisms and are an important energy component obtained from plants. ADP-glucose pyrophosphorylase (ADPGlc Ppase) catalyzes the conversion of glucose-1-phosphate and ATP to ADP-glucose and pyrophosphate and is a key regulated step in both bacterial glycogen and plant starch biosynthesis. ADPGlc Ppase regulation is mediated by the binding of a number of activators and inhibitors, many of which are key metabolic intermediates. This research utilizes the ADPGlc Ppase enzyme from the bacteria Agrobacterium tumefaciens (Ag.t.) that is regulated by fructose- 6-phosphate and pyruvate. This project outlines x-ray crystal structural studies on Ag.t. ADPGlc Ppase to examine substrate binding, allosteric effector binding, and the mechanism of activation. Several roadblocks associated with x-ray crystallography have already been overcome including crystallization and heavy atom derivitization for phase determination. Once the three-dimensional structure of one member of the ADPGlc Ppase protein family is determined homology modeling can be used to construct reasonable structures of the other proteins in the family. As a major control point for the production of renewable and biodegradable carbon sources, ADPGlc Ppase is an attractive enzyme target for protein engineering. Understanding the regulation of the ADPGlc Ppase enzyme family is necessary for the bioengineering of the enzyme and could lead to rational protein engineering of the enzyme to increase starch production
