vasoactive-intestinal-peptide and trimethylenediamine

Bioactive peptides represent an exciting area of research in the fields of biochemistry and medicine and in particular the VIP/PACAP network appears to be of interest. Vasoactive intestinal peptide (VIP) is a pleiotropic factor that exerts a physiological regulatory influence and is involved in the pathogenesis of several human disorders. In this paper we have reported structural characterization of VIP by experimental and computational methods as well as a comparative analysis of the peptide with its transglutaminase catalyzed analog VIP-Diaminopropane (VIP-DAP).

Topics: Animals; Diamines; Humans; Models, Molecular; Solutions; Time Factors; Vasoactive Intestinal Peptide

The structural features of vasoactive intestinal peptide (VIP) and of its Gln16-diaminopropane derivative (VIP-DAP) in solution were investigated by limited proteolysis experiments with trypsin and thermolysin. The proteolysis of the native peptide by both proteinases takes place near the residues in positions 12 and 21/22, suggesting that these amino acids are embedded in segments more flexible than the rest of the molecule. VIP-DAP appears to be more resistant to the proteolytic attack of trypsin, indicating that the derivatization in position 16 is able to stabilize the structure of the peptide. Moreover, the analysis of the mass spectra of the proteolytic mixtures supports the evidence that the derivatization is also able to protect Met17 against oxidation. From these data it can be concluded that VIP in solution under physiological conditions is characterized by the presence of segments with secondary structure, linked together by "hinge" regions that confer flexibility to the peptide, whereas VIP-DAP is embedded in a more rigid conformation, more suitable to receptor interaction.

Topics: Amino Acid Sequence; Diamines; Molecular Sequence Data; Protein Conformation; Solutions; Structure-Activity Relationship; Thermolysin; Trypsin; Vasoactive Intestinal Peptide

The effects of combined administration of vasoactive intestinal peptide (VIP) and the ornithine decarboxylase (ODC) inhibitor, 1,3-diaminopropane (DAP), on development of colon tumors induced by azoxymethane (AOM), on ODC activity of the colon wall, and on the labelling index of colon epithelial cells were investigated in inbred Wistar rats. Rats received weekly subcutaneous injections of AOM for 10 weeks and subcutaneous injections of VIP every other day and drinking water containing DAP (2.5 milligrams) ad libitum until the end of the experiment at week 45. Administration of VIP significantly increased the incidence of colon tumors at week 45. It also resulted in significant increases in colon ODC activity and in the labelling index during administration of AOM, but not after its cessation. Administration of both DAP and VIP significantly reduced the enhanced colon carcinogenesis by VIP. The DAP significantly attenuated the VIP enhancement of colon ODC activity and of the labelling index during AOM administration. These findings indicate that ODC inhibition attenuated enhancement of colon carcinogenesis, and suggest that enhancement of colon carcinogenesis by VIP may be mediated through its polyamine biosynthesis.

Topics: Adenocarcinoma; Adenocarcinoma, Mucinous; Adenoma; Animals; Azoxymethane; Colonic Neoplasms; Diamines; Male; Ornithine Decarboxylase; Ornithine Decarboxylase Inhibitors; Random Allocation; Rats; Rats, Wistar; Vasoactive Intestinal Peptide