Any one of the following cell membrane-permeable peptides (A) to (D) which imparts cell membrane-permeability and mucosal absorbability to hydrophilic physiologically active substances.(A) A peptide comprising an amino acid sequence represented by SEQ ID NO: 1.(B) A peptide comprising an amino acid sequence, that is derived from the amino acid sequence represented by SEQ ID NO: 1 by substitution, deletion, insertion or addition of one or several basic amino acids, and having cell membrane-permeability.(C) A peptide comprising an amino acid sequence, that is derived from the amino acid sequence represented by SEQ ID NO: 1 by substitution, deletion, insertion or addition of one to five amino acids, and having cell membrane-permeability.(D) A peptide comprising an amino acid sequence represented by, for example, a reverse sequence to any one of the sequences (A) to (C), and having cell membrane-permeability.
