N-terminal Early set domain associated with the catalytic domain of chitinase
E or "early" set domains are associated with the catalytic domain of chitinase at the N-terminal end. Chitinases hydrolyze the abundant natural biopolymer chitin, producing smaller chito-oligosaccharides. Chitin consists of multiple N-acetyl-D-glucosamine (NAG) residues connected via beta-1,4-glycosidic linkages and is an important structural element of fungal cell wall and arthropod exoskeletons. On the basis of the mode of chitin hydrolysis, chitinases are classified as random, endo-, and exo-chitinases and belong to families 18 and 19 of glycosyl hydrolases based on sequence criteria. The N-terminal domain of chitinase 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.
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