Purification and amino acid sequences of dog, goat and guinea pig VIPs

VIP has been reported to be identical in pig, cow, human and rat but to differ in four amino acids in chicken. We report now on the purification and sequences of VIP from three other mammalian species, dog, goat and guinea pig (GP). The general method of purification of the three peptides was similar. The frozen intestines were extracted in five volumes of an organic solvent and the residual cakes re-extracted with acid or acid-ethanol. The VIPs were brought to final purity through a series of HPLC steps. Overall recovery using this methodology is in the range of 20-30%. The VIP sequences obtained were: Dog and Goat: (sequence in text) Dog and goat VIP are identical to, but GP VIP differs from, that of other mammalian species. Substitution of the four amino acids in positions 5, 9, 19 and 26 appears not to affect its biological activity. That GP VIP differs from other mammalian VIP's is further evidence that the GP gastroenteropancreatic axis has a unique evolutionary separation from other mammals.