The three-dimensional structure of an endochitinase from barley: ACS Symposium Series

Endochitinases hydrolyze chitin, cleaving glycosidic bonds within the insoluble polymer. Chitin is extremely abundant, being found in the exoskeletons of many insects, crustacea and fungi. Chitinases are of commercial interest since they can be used to create chitin oligomers useful in the chemical, pharmaceutical, and food industries. We have determined the X-ray structure of the chitinase from barley. The model has been refined to high accuracy against 1.8 data. This chitinase has 10 α-helices comprising 47% of the structure. It has a very pronounced cleft, assumed to be the chitin binding and catalytic site. A number of residues, which are conserved within the chitinase family, cluster in this cleft. Presumably they play key roles in chitin binding and hydrolysis. Barley chitinase reveals an ancient resemblance to lysozyme; they share a common central core despite lacking any obvious amino acid sequence similarity. In barley chitinase, Glu 67 appears to act as the proton donor and Glu 89 as the general base in the catalytic mechanism.