Sequence of a new Bowman-Birk inhibitor fromTorresea acreana seeds and comparison withTorresea cearensis trypsin inhibitor (TcTI2)

TaTI (Torresea acreana trypsin inhibitor), a new member of the Bowman-Birk trypsin inhibitor family, was purified from seeds ofTorresea acreana, one of the two known species ofTorresea, a Brazilian native Leguminosae of the Papilionoideae subfamily. Purification was performed by acetone fractionation, anion-exchange chromatography, and gel filtration. The TaTI appears asM _r 7000 in SDS-PAGE under reducing conditions. There are 63 amino acid residues present in the TaTI sequence, which was confirmed by mass spectrometry (8388 daltons). The putative reactive sites residues were Lys-15 and Arg-42 at the first and second site, respectively. The antibodies raised against TcTI2,Torresea cearensis trypsin inhibitor 2, showed a cross-reaction with TaTI, but not with other Bowman-Birk inhibitors purified from Leguminosae. The inhibition constants of TaTI and TcTI2 were comparable when measured against trypsin, chymotrypsin, and factor XIIa, but not on plasmin. The latter was tenfold more effectively inhibited by TcTI2 then by TaTI. Neither TaTI nor TcTI2 affects thrombin, plasma kallikrein, or factor Xa.