A winged bean trypsin inhibitor (WbTI-2) of molecular mass similar to 20 kDa, has been cloned and expressed in Escherichia coli with full activity like the one from seed protein. It completely inhibits trypsin at an enzyme:inhibitor molar ratio of 1:2. PCR with cDNA and genomic DNA using same primers produced about 550 base pair product, which indicated it to be an intronless gene. Through site-directed mutagenesis, the Arg64 has been confirmed as the P1 residue. For the presence of five methionine residues in WbTI-2, cyanogen bromide (CNBr) digestion was carried out. Out of three fragments the one (about 65% of original size) containing the reactive site loop retained 50% activity. (C) 2014 Elsevier Inc. All rights reserved.