| 摘要 |
PROBLEM TO BE SOLVED: To obtain a new substance being a modified substance of natural type ligand against APJ being an orphan G protein conjugated receptor expressed in the central nervous system, circulatory system, immune system, etc., useful as a central nerve function regulator, a circulatory function regulator, an immune function regulator, etc. SOLUTION: This compound is shown by formula I (X1 is H, an amino acid or a peptide comprising 1-25 amino acids; X2 is a neutral amino acid; X3 is a neutral amino acid, an aromatic amino acid or the like; X4 is a direct bond, a neutral amino acid or the like; X5 is an amino acid derivative containing a C end reduced to formyl, a hydroxyl group or the like; with the proviso that cases in which X2 is Leu, X3 is Lys, X4 is Met, X5 is Pro or Pro-Phenol and each amino acid residue of -Arg-Pro-Arg-, -Ser-His- and -Glycol-pro- is nonsubstituted are omitted) such as a compound of formula II. The compound is obtained, for example, by obtaining a natural type ligand by a method for purifying a peptide from human or warm-blooded animal tissue or cell and modifying the ligand.
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