Molecular engineering of a small trypsin inhibitor based on the binding loop of horsegram seed Bowman-Birk inhibitor

Context: The Bowman-Birk inhibitors (BBIs) are currently investigated with renewed interest due to their therapeutic properties in cancer and other inflammatory disease treatment. The molecular mass of the BBI is a limitation, as sufficient amounts of the inhibitor do not reach the organs outside the gastrointestinal tract when administered orally.

Method: The anti-tryptic domain of HGI-III of horsegram (Dolichos biflorus) was cloned using the vector pET-20b (+) and expressed in E. coli BL21 (DE3) pLysS.

Results: Kinetic analysis of this anti-tryptic peptide (recombinant trypsin inhibitory domain (rTID)) reveals that it is a potent inhibitor of trypsin and human tryptase. The K_i (3.2?±?0.17?×?10^?8 M) establishes a very high affinity to bovine trypsin. rTID inhibited human lung tryptase (IC₅₀ 3.78?±?0.23?×?10^?7 M). The rTID is resistant to the digestive enzymes found in humans and animals.

Conclusion: These properties propagate further research on the use of rTID as a therapeutic for cancer and other related inflammatory diseases.