The amino acid sequence of a double-headed trypsin inhibitor from the seeds of Momordica charantia Linn. Cucurbitaceae

A double-headed trypsin inhibitor (MCI-1) was isolated and purified from the seeds of Momordica charantia Linn. Cucurbitaceae, by using the trypsin-sepharose-4B affinity chromatography and CM-Sephadex-C50 ion exchange chromatography. It is composed of 77 amino acid residues: Asp₈ Thr₁ Ser₄ Glu₈ Pro₂ Gly₆ Ala₄ Cys₁₄ Val₂ Met₄ Ile₈ Leu₁ Phe₁ His₃ Lys₄ Arg₇. The amino acid sequence of MCI-1 was determined by sequencing the cyanogen bromide, tryptic and staphylococcus aureus V8 proteolytic peptides, then aligned by overlapped sequences. The result shows that MCI-1 contains 7 pairs of disulfide bonds, its sequence showed the high homology with those of “Bowman-Birk” inhibitors. About 50% trypsin inhibitory activity still remained after MCI-1 was cleavaged with cyanogen bromide.