Chitinase

Definition

A hydrolytic enzyme that cleaves glycosidic bonds in chitin, catalyzing the breakdown of N-acetyl-β-D-glucosaminide (1→4)-β-linkages in chitin polymers and chitodextrins. In arthropods, chitinases are essential for remodeling the exoskeleton during ecdysis, degrading old cuticle, and in some species for digesting chitinous prey or defending against entomopathogenic fungi.

Etymology

From chitin (the structural polysaccharide of arthropod cuticle and fungal cell walls) + -ase (enzyme suffix)

Example

During molting in the tobacco hornworm (Manduca sexta), chitinases secreted by the molting fluid dissolve the endocuticle, allowing the old exoskeleton to split and the soft new cuticle to expand.

Related Terms

• Chitin
• Ecdysis
• Cuticle
• Exoskeleton
• molting fluid
• N-acetylglucosamine
• chitobiase
• peritrophic matrix
• entomopathogenic fungi
• host-pathogen interactions

Usage Notes

Chitinases occur across kingdoms: arthropods produce them for cuticle turnover; plants and microbes produce them for defense against chitin-containing pathogens. In entomology, distinguish endogenous chitinases (molting, digestion) from exogenous ones (fungal virulence factors, biocontrol agents). Some insects upregulate chitinase expression in response to fungal infection as a counter-defense. The term is sometimes used loosely for chitobiases and N-acetylglucosaminidases, which complete chitin depolymerization; specialists may specify 'true chitinase' (endo-splitting) versus exo-acting chitobiosidases.