A porcine brain polypeptide is identical to the vasoactive intestinal polypeptide.

The polypeptide known as the "vasoactive intestinal polypeptide" has now been isolated from porcine brain. Determination of the structure shows that cerebral vasoactive intestinal polypeptide consists of 28 amino acid residues in the sequence: His-Ser-Asp-Ala-Val-Phe-Thr-Asp-Asn-Tyr-Thr-Arg-Leu-Arg-Lys-Gln-Met-Ala-Val-Lys -Lys-Tyr-Leu-Asn-Ser-Ile-Leu-Asn-NH2. This structure is identical to that of vasoactive intestinal polypeptide previously isolated from porcine and bovine upper intestine, and its amino acid composition is identical to that of human vasoactive intestinal polypeptide from colon. Although immunoreactive vasoactive intestinal polypeptide has been shown previously to be present in different tissues, this is the first time it has actually been isolated from cerebral tissue, or indeed from any nonintestinal tissue.