Putative catalytic domain of chitin deacetylase-like proteins
Chitin deacetylases (CDAs, EC 3.5.1.41) are secreted metalloproteins belonging to a family of extracellular chitin-modifying enzymes that catalyze the N-deacetylation of chitin, a beta-1,4-linked N-acetylglucosamine polymer, to form chitosan, a polymer of beta-(1,4)-linked d-glucosamine residues. CDAs have been isolated and characterized from various bacterial and fungal species and belong to the larger carbohydrate esterase 4 (CE4) superfamily. This family includes many midgut-specific CDA-like proteins mainly from insects, such as Tribolium castaneum CDAs (TcCDA6-9). These proteins contain a putative CDA-like catalytic domain similar to the catalytic NodB homology domain of CE4 esterases. In addition to the CDA-like domain, some family members have an additional chitin-binding peritrophin-A domain (ChBD).