Neuropeptides derived from prosomatostatin that do not contain the somatostatin-14 sequence.

Two neuropeptides reacting with antibodies directed against the C-terminal region of somatostatin 28(1-12) were purified to homogeneity from rat brain extracts. Amino acid analysis revealed that the larger peptide (8 kdaltons) consisted of 76 amino acids. Microsequencing established its aminoterminal structure as: Ala-Pro-Ser-Asp-Pro-Arg-Leu-Arg-Gln-Phe-X-Gln-Lys. The 8 kdalton somatostatin 28(1-12)-like peptide corresponds to the whole prosomatostatin molecule without Arg-Lys-somatostatin-14. The smaller peptide (5 kdaltons) consists of 44 amino acids and is generated after cleavage of a Leu-Leu bond at position 56-57 of pre-prosomatostatin. Both 8 kdalton and 5 kdalton somatostatin 28(1-12)-like peptides contain somatostatin 28(1-12) at their C-termini. The 4 most abundant neuropeptides derived from pre-prosomatostatin (pre-proSS) and presently characterized are: somatostatin-14, somatostatin 28(1-12), somatostatin 28 and pre-proSS25-100.