A peptide of the following (I) or (II).(I) a peptide represented by the formula B, A-B, B-C orA-B-C in which A, B and C each is represented by the following(1), (2) and (3) and, when it is bonded to other object peptide,it is able to extent the half-life in plasma as compared withthe object peptide where the physiological activity of theobject peptide is still retained.(II) a peptide comprising a reversed sequence of thepeptide of (I)； a sequence which is represented by A-B in (I)and A or B is reversed； a sequence which is represented by B-Cin (I) and B or C is reversed； or a sequence which is representedby A-B-C in (I) and A, B, C, A and B, B and C or A and C isreserved.(1) A is a peptide comprising 1 to 14 of any amino acid(s)(2) B is a peptide represented by the formula 1:(Wk-Xl-Y-Zm-Wn)-(Wo-Xp-Y-Zq-Wr)s(In the formula 1, W is a basic amino acid； X and Z areany amino acids； Y is an acidic amino acid； k is 1 or 2； l isan integer of 4 >；= l >；= 0； m is an integer of 2 >；= m>；= 0； 4 >；= l+ m >；= 0； n is 1 or 2； o is 1 or 2； p is an integer of 4 >；= p>；= 0； q is an integer of 2 >；= q >；= 0； 4 >；= p + q>；= 0； r is 1 or2； and s is 0 or 1.)(3) C is a peptide comprising 2 to 14 of any amino acids.
