This domain is found on the very N-terminal of eukaryotic variants of the glycogen debranching enzyme (GDE), where it is immediately followed by the aldolase-like domain. The eukaryotic GDE performs two functions: 4-alpha-D-glucanotransferase, EC:2.4.1.25, and Amylo-alpha-1,6-glucosidase, EC:3.2.1.33, performed by the, respectively N- and C- terminal halves of eukaryotic GDE enzyme. The domain is involved in the glucosyltransferase activity, probably as a substrate-binding module (by analogy with other glucosyltransferases).