ISOLATION AND ACTIVITIES OF THE TRYPSIN-MODIFIED VICIA-ANGUSTIFOLIA PROTEINASE-INHIBITOR LACKING CARBOXYL-TERMINAL HEXAPEPTIDE

The Vicia angustifolia proteinase inhibitor was incubated with p-toluenesulfonyl-l-phenylalanine chloromethyl ketone-trypsin (EC 3.4.21.4) and a main product was isolated. The purified product was different to the first trypsin-modified V. angustifolia inhibitor. The C-terminal residues of the new derivative were arginine, which was also the C-terminal of the cleaved anti-tryptic site; lysine was a newly exposed C-terminal. These results suggest that the new derivative lacks the C-terminal portion of the native inhibitor, which has asparagine at its C-terminus. The liberated C-terminal peptide had the following amino acid sequence: H-Glu-Glu-Val-Ile-Lys-Asn-OH. The derivative lacking the C-terminal hexapeptide still possesses inhibitory activities against trypsin and α-chymotrypsin (EC 3.4.21.1), however, its antichymotryptic activity was inactivated by incubation with chymotrypsin at pH 8.0. © 1979.