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 resis tant as well as susceptible cultivars of chickpea (Cicer arietinum L.) inoculated with Ascochyta rabiei. Leaves of resistant cultivars exhib ited an about five-fold increase on the 6th day of inoculation, as com pared with the uninoculated control. Although a similar pattern of cha nges in enzyme activity was discerned with the susceptible cultivar al so, the magnitude of induction was low. Compared with leaves, the exci sed inoculated pods showed a rapid and early increase in chitinase act ivity. Chitinase was purified from leaves and pods of inoculated chick pea resistant cultivar 30- and 33-fold, respectively, by heat treatmen t, ammonium sulfate fractionation, gel filtration and affinity chromat ography on regenerated chitin. Except for the molecular weight (leaf, 30 kD; pod 27 kD), the enzyme from both sources had the same propertie s 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+.