This is a glucanotransferase catalytic domain of the eukaryotic variant of the glycogen debranching enzyme (GDE). The eukaryotic GDEs 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 enzymes. The domain is a catalytic domain responsible for the glucanotransferase function. It belongs to the alpha-amylase clan and is predicted to have a structure of a 8-stranded alpha/beta barrel (TIM barrel) where strands are interrupted by long loops and additional mini-domains. In most other amylases, the catalytic domain is followed by a beta- barrel substrate binding domain, but presence of such a domain cannot be verified in the human (and other eukaryotic) GDE enzymes.