Dextransucrase catalyzes the formation of a glucan containing Alpha 1-6 and Alpha 1-3 bonds. The glucan, dextran, is a major component of dental plaque and is formed by the action of the enzyme on sucrose. Studies are proposed that will extend work that is currently in progress. Elements of the reaction pathway will be studied to evaluate the physiological importance of two alternate pathways of polymer formation. Similarly, the significance of the reversibility of these reactions will be assessed. The mechanism involved in the formation of the two bond types is to be studied along with the question of whether this is a regulated process. The active site of the enzyme is to be probed by use of chemical modifying agents. In addition, compounds that may serve as active-site directed inactivators will be synthesized and studied. The enzyme has been shown to have unique behavior with detergents. In the presence of SDS it is completely inactivated, and upon the addition of Triton X-100 it is completely reactivated. Studies are planned that will explore the molecular events associated with this behavior.
