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Chitin/cellulose binding domains of chitinase and related enzymes This group contains proteins related to the cellulose-binding domain of Erwinia chrysanthemi endoglucanase Z (EGZ) and Serratia marcescens chitinase B (ChiB). Gram negative plant parasite Erwinia chrysanthemi produces a variety of depolymerizing enzymes to metabolize pectin and cellulose on the host plant. Cellulase EGZ has a modular structure, with an N-terminal catalytic domain linked to a C-terminal cellulose-binding domain (CBD). CBD mediates the secretion activity of EGZ. Chitinases allow certain bacteria to utilize chitin as a energy source. Typically, non-plant chitinases are of the glycosidase family 18. Bacillus circulans Glycosidase ChiA1 hydrolyzes chitin and is comprised of several domains: the C-terminal chitin binding domain, an N-terminal catalytic domain, and 2 fibronectin type III-like domains. Bacillus circulans WL-12 ChiA1 facilitates invasion of fungal cell walls. The ChiA1 chitin binding domain is required for the specific recognition of insoluble chitin. although topologically and structurally related, ChiA1 lacks the characteristic aromatic residues of Erwinia chrysanthemi endoglucanase Z (CBD(EGZ)). Streptomyces griseus Chitinase C is a family 19 chitinase, and consists of a N-terminal chitin binding domain and a C-terminal chitin-catalytic domain that effects degradation. ChiC contains the characteristic chitin-binding aromatic residues. Chitinases function in invertebrates in the degradation of old exoskeletons, in fungi to utilize chitin in cell walls, and in bacteria which use chitin as an energy source. |
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Jiyao W et al.(2023). "The conserved domain database in 2023.",