A thermotolerant protein with trypsin inhibitory activity designated as CaTI was purified to homogeneity from
seeds of Cassia absus. Gel filtration chromatography and SDS-PAGE analysis showed the apparent molecular mass of
~20 kDa. Partial internal sequences indicate that CaTI belongs to Kunitz-inhibitor family. CaTI inhibits the bovine trypsin
in 1:1 molar ratio and exhibited a competitive-type inhibitory activity with Ki = 5.6 10-9 M. The inhibitory activity was
retained over a broad pH range (2-12). Thermal stability study showed that it is stable up to 80 °C and inhibition activity
reduced at and above 90 °C which might be due to the presence of predominantly β-sheets revealed by the CD study. The
proteolysis studies of CaTI exhibited strong resistance to proteolysis by different proteases tested. The studies show that
CaTI can be used as potential candidates for the development of the transgenic plant against the microbes and insect pests.
Keywords: Cassia absus, Caesalpiniaceae, Kinetic study, Stability studies, Trypsin inhibitor.
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