PRIMARY STRUCTURE AND ALLERGENIC ACTIVITY OF TRYPSIN-INHIBITORS FROM THE SEEDS OF BUCKWHEAT (FAGOPYRUM-ESCULENTUM MOENCH)

The complete amino acid sequences of two trypsin inhibitors BWI-2a and BWI-2b from the seeds of buckwheat (Fagopyrum esculentum Moench) were determined. BWI-2b consists of 51 amino acid residues containing two disulfide bonds. BWI-2a shares all amino acids with BWI-2b except for the C-terminal tripeptide: BWI-2a lacks Glu-Gly-Asn and ends with the Asp residue, making a total of 48 residues in the chain. The two disul fide bonds connect Cys(11) to Cys(32) and Cys(15) to Cys(28), BWI-2b s hows no relatedness to the other buckwheat trypsin inhibitor reported [Belozersky et al. (1995) FEES Lett, 371, 264-266]. Sequence compariso n of BWI-2b with those of the other proteins included in PIR showed th at BWI-2b is significantly homologous to the N-terminal region of stor age proteins classified in the vicilin family. Furthermore, the allerg enic activity of BWI-2b and the other buckwheat trypsin inhibitor BWI- 1 was examined using the radioallergosorbent test. The result indicate d that both inhibitors BWI-2b and BWI-1 have IgE binding activity, alb eit to a low extent, suggesting that they might be minor allergenic pr oteins in buckwheat seeds.