N-terminal Early set domain associated with the catalytic domain of cyclomaltodextrinase and pullulan-degrading enzymes
E or "early" set domains are associated with the catalytic domain of the cyclomaltodextrinase (CDase) and pullulan-degrading enzymes at the N-terminal end. Members of this subgroup include CDase, maltogenic amylase, and neopullulanase, all of which are capable of hydrolyzing all or two of the following three types of substrates: cyclomaltodextrins (CDs), pullulan, and starch. These enzymes hydrolyze CDs and starch to maltose and pullulan to panose by cleavage of alpha-1,4 glycosidic bonds whereas alpha-amylases essentially lack activity on CDs and pullulan. They also catalyze transglycosylation of oligosaccharides to the C3-, C4- or C6-hydroxyl groups of various acceptor sugar molecules. The N-terminal domain of the CDase and pullulan-degrading enzymes may be related to the immunoglobulin and/or fibronectin type III superfamilies. These domains are associated with different types of catalytic domains at either the N-terminal or C-terminal end and may be involved in homodimeric/tetrameric/dodecameric interactions. Members of this family include members of the alpha amylase family, sialidase, galactose oxidase, cellulase, cellulose, hyaluronate lyase, chitobiase, and chitinase, among others.
Jiyao W et al.(2023). "The conserved domain database in 2023.",