Study of a possible structural relationship between thymopoietin and the facteur thymique serique

Background peptide chemistry, and the known 49-amino acid sequence of thymopoietin and the known 9-amino acid sequence of the facteur thymique serique (FTS) allowed the concept that Arg⁴⁹ of thymopoietin might be linked to Gln¹ of FTS in a new 58-amino acid peptide in tissue. Cleavage between Arg⁴⁹ and Gln⁵⁰ adjacent to the unique Lys⁴⁸-Arg⁴⁹ moiety could liberate thymopoietin and the H-Gln¹]-FTS which could cyclize to FTS by the known reaction. In support of, rather than negating, this concept, synthetic FTS and the new dodecapeptide consisting of Val-Lys-Arg linked to the N-terminal of H-Gln¹]-FTS showed comparable immune stimulating activity, $\text{in vivo}$; both peptides appeared more active than synthetic thymopoietin II.