Glucansucrases are relatively large (-160 kDa) extracellular enzymes produced by lactic acid bacteria. Using sucrose as a substrate they synthesize high molecular mass glucose polymers, called a-glucans, which allow the bacteria to adhere to surfaces and create a biofilm. The glucan polymers are of importance for the food and dairy industry as thickening and jellying agents. An overview is given of the current insights into the structure and functioning of these and related enzymes Keywords: glucansucrase; amylosucrase; crystal structure; catalysis; catalytic mechanism. B. W. Dijkstra and A. VujiCi6-Zagar; Laboratory of Biophysical Chemistry, University ofGroningen Nijenborgh 4,9747 AG Groningen, The Netherlands
