C-terminal Early set domain associated with the catalytic domain of chitobiase (also called N-acetylglucosaminidase)
E or "early" set domains are associated with the catalytic domain of chitobiase at the C-terminus. Chitobiase digests the beta, 1-4 glycosidic bonds of the N-acetylglucosamine (NAG) oligomers found in chitin, an important structural element of fungal cell wall and arthropod exoskeletons. It is thought to proceed through an acid-base reaction mechanism, in which one protein carboxylate acts as the catalytic acid, while the nucleophile is the polar acetamido group of the sugar in a substrate-assisted reaction with retention of the anomeric configuration. The C-terminus of chitobiase may be related to the immunoglobulin and/or fibronectin type III superfamilies. E set 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.",