This entry represents a domain found in prokaryotic alpha-amylase and 4-alpha-glucanotransferase. It adopts a beta-sandwich fold, in which two layers of anti-parallel beta-sheets are arranged in a nearly parallel fashion. The exact function of this family is, as yet, unknown, however it has been proposed that they may play a role in transglycosylation reactions [1].

1: Crystal structures of 4-alpha-glucanotransferase from Thermococcus litoralis and its complex with an inhibitor. Imamura H, Fushinobu S, Yamamoto M, Kumasaka T, Jeon BS, Wakagi T, Matsuzawa H; J Biol Chem. 2003;278:19378-19386. PMID:12618437