Abstract The glg gene cluster of the E. coli encodes the enzymes necessary for glycogen synthesis, which is a series of three enzyme-catalyzed reactions. This pathway begins with a phosphoralated glucose that is activated with adenosine triphosphate (ATP) via the adenosine diphosphate pyrophorylase (ADP Glc PPase) enzyme. Next, this product is added to the end of the growing glucan chain by the glycogen synthase enzyme. The chain is then modified to glycogen via the branching enzyme. This branching enzyme synthesizes the amylopectine a-1,6-D-glycosyl linkages from the rearrangement of the a-1,4-glucan. We specifically work with the branching enzyme, which we study via DNA and protein work. To study this enzyme, we have performed mutagenisis, sequencing, expression, purification, assays, and crystallization. By these means we hope to find the structure-function relationship of the branching enzyme.