DES—Nα—ACETYL—α—MELANOTROPIN:1

Application of the 2-methylsulfonylethyloxycarbonyl group for temporary amino protection enables the synthesis from one precursor of des-Nα1-acetyl-α-MSH, the two mono N-acetylated forms (in positions I and II) and the diacetyl form of this tridecapeptide amide. The free tridecapeptide amide, although structurally unrelated to the normal substrate, was recognized by an enzyme occurring in calf eye-lens tissue. The product of the enzymatic reaction was exclusively α-MSH. Partial sequences derived from the N-terminus were less rapidly acetylated or not at all, depending on their chain length. The enzyme, therefore, appears to direct its activity to free N-terminal α-amino groups of peptides exceeding a certain critical chain length. Acetylation of -amino functions did not occur.