VIP 5mg

Vasoactive intestinal peptide is a 28-residue, C-terminally amidated neuropeptide with 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 (HSDAVFTDNYTRLRKQMAVKKYLNSILN-NH2), encoded by the VIP gene on chromosome 6q25.2 (UniProt P01282). The C-terminal amide is not incidental — it is required for binding at this receptor class. VIP belongs to the secretin/glucagon/PACAP superfamily and shares roughly 68 percent homology with PACAP (Miyata et al., 1989, PMID 2803320), but the two are distinct peptides from distinct genes: VIP from VIP on chromosome 6, PACAP from ADCYAP1 on chromosome 18. The synthetic peptide carries the nonproprietary name aviptadil and is the identical 28-mer rather than an analog.

One identity caution is worth recording because it affects the numbers most sources print. PubChem and ChEMBL publish a free-acid molecular formula and mass against the amidated sequence, so the formula and mass in those records do not describe the native peptide — converting the C-terminus to the amide loses an oxygen and gains a nitrogen and a hydrogen. The amidated values are the correct ones. A separate PubChem record carrying D-tyrosine and allo-residues describes a stereochemically different molecule and should not be used for this compound.

The receptor pharmacology is well characterized. VIP acts at two class B G-protein-coupled receptors, VPAC1 (gene VIPR1) and VPAC2 (gene VIPR2), coupling primarily through Gs to adenylyl cyclase and cyclic AMP; its affinity at the related PAC1 receptor is several hundred-fold lower, so it behaves effectively as a VPAC1/VPAC2 dual agonist (Harmar et al., British Journal of Pharmacology 2012, PMID 22289055). Its documented physiological roles in animal models include smooth-muscle relaxation and vasodilation, stimulation of epithelial water and electrolyte secretion, and circadian signaling in the suprachiasmatic nucleus — the last supported by the strongest genetic evidence in the field, since mice lacking the VPAC2 receptor fail to sustain circadian rhythms (Harmar et al., Cell 2002, PMID 12086606), a phenotype echoed in VIP-deficient mice (Nature Neuroscience 2005, PMID 15750589).

A frequent misreading is worth heading off: the "VIP interneurons" of cortical neuroscience are cells identified by the fact that they express the VIP gene, and their signaling is GABAergic. That literature describes those cells, not the actions of the peptide as a reagent. As a practical matter for laboratory work, VIP is also extremely short-lived — an initial plasma half-life on the order of one to two minutes in published animal and ex vivo work — and is cleaved by mast-cell tryptase and by neprilysin. It is not a substrate for DPP-4, contrary to a common assumption: VIP carries serine at position 2, and that enzyme requires proline or alanine there (PMID 8100523). VIP is not an approved drug, and this product is supplied strictly for in vitro and laboratory research and is not for human or veterinary use.