Amino Acids and Peptides. XVII. Synthesis of a Tridecapeptide Corresponding to the Sequence 165-177 of T-Kininogen (Tryptic Peptide) Containing Gln-Val-Val-Ala-Gly Sequence and the Relationship between Structure and Effect on Thiol Proteinase

The tridecapeptide corresponding to the sequence 165-177 of T-kininogen (tryptic peptide) (I) containing Gln-Val-Val-Ala-Gly sequence was synthesized by a conventional solution method and its effect on thiol proteinase was examined. Although Z-Gln-Val-Val-Ala-Gly-OMe showed inhibitory activity towards papain and protective activity against T-kininogen-induced inhibition of papain, the tryptic peptide obtained did not exhibit any effect on thiol proteinase. In order to study the relationship between structure and effect on thiol proteinase, several compounds (II-VI) modified with various groups at the N-terminus of the Gln-Val-Val-Ala-Gly sequence were synthesized. Peptides V and VI, which have an aromatic ring at the N-terminus, exhibited weak inhibitory and significant protective activities. A small peptide such as Gln-Val-Val-Ala-Gly might be better able to approach papain than the tryptic peptide (I), and the aromatic ring associated with Gln-Val-Val-Ala-Gly at the N-terminus apparently strengthened the binding ability of the peptide to papain.