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 disulfi de bridges. The active site is related in structure to animal and viral lys ozymes. However, unlike in lysozyme, the architecture of the active site su ggests a single-step cleavage. According to this mechanism, Glu68 is the pr oton donor and Glu90 assists in the reaction by moving towards the substrat e and recruiting a water molecule that acts as the nucleophile. In this mod el, 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.