PEPTIDE AND ITS SALT

PROBLEM TO BE SOLVED: To obtain a new peptide comprising a specific peptide having a specified amino acid sequence, selectively cleaved by thrombin, useful as a constituting element, etc., of detection system of the thrombin and a thrombin-responsive material and excellent in safety. SOLUTION: This peptide is the new one (salt) of the formula (X is an amino acid residue selected from Gly and Ala, a peptide fragment composed of 2-5 Gly and/or Ala, or a single bond; Y is an amino acid residue, a peptide fragment composed of 2-5 amino acid residues such as Pro-Ala, Gly-Ala, Pro-Ala-Gly-Gly and Gly-Ala-Gly-Gly, or a single bond), selectively cleaved by thrombin and useful as a constituting element, etc., of detection system of the thrombin, a thrombin-responsive material, etc. The peptide is obtained by performing a solid synthesizing method of a peptide according to the amino acid sequence of the peptide having thrombin-cleavability and shown by the formula.