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 (IC(50) 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.