INDUCTION, PURIFICATION AND CHARACTERIZATION OF CHITINASES FROM CHICKPEA (CICER-ARIETINUM L) LEAVES AND PODS INFECTED WITH ASCOCHYTA-RABIEI

Chitinase (EC 3.2.1.14) activity increased in leaves and pods of resistant as well as susceptible cultivars of chickpea (Cicer arietinum L.) inoculated with Ascochyta rabiei. Leaves of resistant cultivars exhibited an about five-fold increase on the 6th day of inoculation, as compared with the uninoculated control. Although a similar pattern of changes in enzyme activity was discerned with the susceptible cultivar also, the magnitude of induction was low. Compared with leaves, the excised inoculated pods showed a rapid and early increase in chitinase activity. Chitinase was purified from leaves and pods of inoculated chickpea resistant cultivar 30- and 33-fold, respectively, by heat treatment, ammonium sulfate fractionation, gel filtration and affinity chromatography on regenerated chitin. Except for the molecular weight (leaf, 30 kD; pod 27 kD), the enzyme from both sources had the same properties with an optimum pH of 5.0, optimum temperature of 37 degrees C and a Km value of 0.65 mg chitin mL(-1). The enzyme had no requirement for any of the metal ions, and rather was inhibited by Hg2+.