Structure of jack bean chitinase

The structure of jack bean chitinase was solved at 1.8 Angstrom resolution by molecular replacement. It is an alpha-helical protein with three disulfide bridges. The active site is related in structure to animal and viral lysozymes. However, unlike in lysozyme, the architecture of the active site suggests a single-step cleavage. According to this mechanism, Glu68 is the proton donor and Glu90 assists in the reaction by moving towards the substrate and recruiting a water molecule that acts as the nucleophile. In this model, a water molecule was found in contact with Glu90 O-epsilon 1 and Thr119 O-gamma at a distance of 3.0 and 2.8 Angstrom, respectively. The model is in accordance with the observed inversion mechanism.