Characterisation of a Trypsin/Chymotrypsin Inhibitor from Jack Fruit (Artocarpus integrifolia) Seeds

Jackfruit seed (Artocarpus integrifolia Hook8 trypsin inhibitor (JSTI) was
found to be rich in acidic amino acids and devoid of free thiol groups. The
N-terminal and C-terminal amino acids of JSTI were aspartic acid and
serine, respectively. The inhibitor was stable under conditions of extremes
of pH (3.0-12.0), at high temperatures and in the presence of denaturing
agents. JSTI showed a non-competitive type of inhibition with Kt values of
0.48 rt 0.1 7 nM and 0.16 rf: 0.04 nMfor trypsin and chymotrypsin, respectively.
The JSTI-trypsin complex exhibited chymotrypsin inhibitory activity
suggesting the 'double-headed' nature of the inhibitor. Chemical moduication
of lysine residues resulted in loss of trypsin and chymotrypsin inhibitory
activities of JSTI indicating that amiizo groups are essential for activity