An antifungal peptide from Fagopyrum tataricum seeds

A major trypsin inhibitor was isolated and characterized from the seeds of the tartary buckwheat (Fagopyrum tataricum) (FtTI) by ammonium sulfate precipitation, ion exchange chromatography and centrifugal ultrafiltration. SDS-PAGE analysis under reducing condition showed that FtTI is a single polypeptide chain with a molecular mass of approximately 14 kDa. The complete amino acid sequence of FtTI was established by automatic Edman degradation and mass spectrometry. It was found that the trypsin inhibitor molecule consists of 86 amino acid residues containing two disulfide bonds which connect Cys8 to Cys65 and Cys49 to Cys58. The active site of the inhibitor was found to contain an Asp66–Arg67 bond. MALDI-TOF analysis showed that FtTI has two isoforms (Mr: 11.487 and 13.838 kDa). Dixon plots revealed a competitive inhibition of trypsin with inhibition constants (Ki) of 1.6 nM. Analysis of the amino acid sequence suggests that FtTI is a member of the protease inhibitor I family. What is more, FtTI exhibited strong inhibitory activity against phytopathogenic fungi.

► The complete amino acid sequence of FtTI has been established by automatic Edman degradation and mass spectrometry.
► The molecule of inhibitor consists of 86 amino acid residues containing two disulfide bonds which connect Cys8 to Cys65 and Cys49 to Cys58.
► The active site of the inhibitor contains an Asp66–Arg67 bond.
► Dixon plots revealed a competitive inhibition of trypsin with inhibition constants (Ki) of 1.6 nM.
► FtTI exhibited strong inhibitory activity against phytopathogenic fungi.