ISOLATION AND AMINO-ACID-SEQUENCES OF 2 TRYPSIN-INHIBITORS FROM THE SEEDS OF BITTER GOURD (MOMORDICA-CHARANTIA)

Two novel trypsin inhibitors, MCTI-II' and BGIT, were isolated from th e seeds of bitter gourd (Momordica charantia) and their amino acids se quenced. MCTI-II' was a squash type trypsin inhibitor and lacked the N -terminal arginine residue of Momordica charantia trypsin inhibitor (M CTI)-II. It consists of 27 amino acid residues and forms a dimeric str ucture. BGIT had 88% homology with bitter gourd inhibitor against an a cidic amino acid-specific endopeptidase (BGIA) consisting of 68 amino acid residues and inhibited not only trypsin but also subtilisin Carls berg. The amino acid replacements occurred in 8 positions of which tha t of Gln2 by Arg or of Ala44 by Lys is suggested to be responsible for the trypsin-inhibitory action of BGIT. Inhibitory activity of BGIT fo r trypsin was greatly decreased by acetylation, while that for subtili sin was slightly increased. From these results and the sequence compar ison with eglin-c superfamily inhibitos, the reactive site of BGIT is assumed to be Lys44.