Brassica junceachitinase is an endo-acting, pathogenesis-related protein that is classified into glycoside hydrolase family 19, with highest homology (50–60%) in its catalytic domain to class I plant chitinases. Here we report X-ray structures of the chitinase catalytic domain from wild-type (apo,as well as with chloride ions bound) and a Glu234Ala mutant enzyme, solved by molecular replacement and refined at , and A˚ resolution, respectively.