[Arg³]substance P and neurokinin A from chicken small intestine

Using antisera specific for NH₂-terminal and COOH-terminal regions of substance P and for the COOH-terminal region of neurokinin A, peptides with tachykinin-like immunoreactivity were isolated from extracts of chicken small intestine. The peptide Arg-Pro-Arg-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ differs from human substance P by substitution of the lysyl residue by an arginyl residue at position 3. Synthetic [Arg³]substance P showed identical chromatographic and immunochemical properties to chicken substance P and was equipotent with substance P in contracting the guinea pig ileum. A second peptide His-Lys-Thr-Asp-Ser-Phe-Val-Gly-Leu-Met-NH₂ isolated from the extracts is identical to human neurokinin A. A third peptide was immunoreactive towards the COOH-terminally directed antiserum to substance P only but was not characterized structurally in this study.