Sa. Godbole et al., FURTHER CHARACTERIZATION OF PROTEASE INHIBITORS FROM PIGEON PEA (CAJANUS-CAJAN (L) MILLSP) SEEDS, Journal of the Science of Food and Agriculture, 64(3), 1994, pp. 331-335
Cajanus trypsin inhibitor (CTI) and Cajanus trypsin-chymotrypsin inhib
itor (CTCI) previously purified from cv TAT-10 were further characteri
sed. The modification of the inhibitors revealed the presence of lysin
e at the trypsin reactive site in both CTI and CTCI. Modification of t
yrosine at the reactive site of CTCI did not abolish chymotrypsin inhi
bition suggesting the presence of leucine or phenylalanine as reported
in other chymotrypsin inhibitors. CTCI did not contain tryptophan. Di
ssociation constants for the inhibitors with bovine trypsin were in th
e region of 0.69 nmol (CTCI) and 0.029 nmol (CTI). Although the protea
se inhibitors lost their inhibitory activity on exposure to 2-mercapto
ethanol they remained attached to the enzyme. The inhibitors were not
very effective against the protease from Helicoverpa armigera which is
a serious field pest of Cajanus. Dissociation constants for the inhib
itors with the larval enzyme were in the region of 100 nmol.